CLAIM FOR PRIORITY

[0001] This application is a continuation of U.S. Patent Application No. 16/147,634, filed on September 29, 2018, titled“DUAL POWER I/O TRANSMITTER,” and which is incorpo rated by reference in entirety.

BACKGROUND

[0002] Next generations memory (DDR - Double Data Rate) technologies (e.g. LP4x,

DDR5, LP5, etc.) have been purposed for lower area and lower power. The Input / Output (I/O) supply voltage is going down (e.g., to about 0.3V, 0.6 V, etc.) accordingly. With such low I/O voltage, traditional driver (e.g., p-type metal oxide semiconductor (PMOS) pull-up and n-type MOS (NMOS) pull-down) may not be used for area and power (even non functional in some process node corners), e.g., as the PMOS pull-up may run into over-drive issue (e.g., V _gs gets smaller). In addition, from reusability perspective, it is desirable to have combo transmitters to support both high voltage DDR4 (e.g., at a voltage level of about 1.2V or higher) and low voltage LP4x/LP5, DDR5 (e.g., at a voltage level of about 0.3 V) using the same physical design (PHY). To comply with EoS (Electrostatic Overstress) using thin gate device at 1.2V supply, stacked devices are used, which makes over-drive issue of the PMOS pull-up even worse.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The embodiments of the disclosure will be understood more fully from the de tailed description given below and from the accompanying drawings of various embodiments of the disclosure, which, however, should not be taken to limit the disclosure to the specific embodiments, but are for explanation and understanding only.

[0004] FIG. 1 illustrates a schematic of a Memory/Controller interface.

[0005] FIG. 2 illustrates a schematic of a memory controller transmitter with stacked

P over N design, according to some embodiments of the current invention.

[0006] FIG. 3 illustrates a schematic of a Double Data Rate (DDR) driver circuitry, according to some embodiments of the disclosure.

[0007] FIG. 4 illustrates a schematic of a Low Power Double Data Rate (LPDDR) driver circuitry, according to some embodiments of the disclosure. [0008] FIG. 5 illustrates a schematic of a pull-up pre-driver, according to some em bodiments of the disclosure.

[0009] FIGs. 6A-6B illustrate two different conventional transmitter output stage to pologies.

[00010] FIG. 7 illustrates a pn-over-n transmitter output stage according to some em bodiments.

[00011] FIG. 8A illustrates a test setup for testing different output stage topologies.

[00012] FIG. 8B illustrates a pulse response output for n-n, p-n and pn-n topologies.

[00013] FIGs. 9A and 9B illustrate a post-layout simulation result of the pull-up and pull-down impedances of the output stage across three process comers, according to some embodiments.

[00014] FIG. 10 illustrates a mobile computing platform and a data server machine employing the memory controller transmitter, in accordance with some embodiments.

[00015] Fig. 11 illustrates a smart device or a computer system or a SoC (System-on- Chip) employing the memory controller transmitter, according to some embodiments of the disclosure.

DETAILED DESCRIPTION

[00016] Current implementations of LPDDRx compliant transmitter output stage use a combination of device on-resistance (R_on) and resistance (e.g., approximately 25% device and approximately 75% resistor) to achieve the pull-up and pull-down impedance in the transmitter. Large devices are used to realize the 25% contribution to pull-up and pull-down impedances. These large devices result in increased capacitance on the input-output (I/O) pad coupled to the transmitter output stage. The increased pad capacitance limits the maximum operable data-rate of the transmitter (note, current LPDDRx products operate up to 3.2 Giga bits per second (Gb/s)). Furthermore, it is desirable that the LPDDRx configurations of the transmitter output stage (e.g., for client segment) operate over a wide range of power supply voltages (e.g., V _ddq between about 0.3V to about 0.7V). Implementations using n-over-n de vice transmit topology offer relatively high output swing, relatively low power dissipation, and relatively high linearity, e.g., merely at lower supply voltages (e.g., 0.3V), but have lim ited voltage swing at higher supply voltages and poor slew rate during pull-up operation. To meet the target voltage swing and slew rate specifications, these circuit topologies rely on increasing pre-driver supply voltage to achieve higher output voltage swing, but this leads to increased power dissipation. [00017] Some embodiments of the current disclosure implement dual power a device- only transmitter to minimize area, pad capacitance and enable operation of the interface at higher frequencies (e.g., 10 Gb/s or more). The embodiments meet the target swings without having to use an elevated pre-driver supply voltage when the output stage of the transmitter is operating at a higher power supply voltage V _ddq , thereby reducing power dissipation. The embodiments also improve slew rate during pull-up (e.g., during the output driver data transi tion from logic low to logic high).

[00018] Some embodiments of the disclosure comprise NMOS transistor(s) in the pull- up driver, which solves the issues of supporting low I/O supply voltage. The gate voltage of the NMOS pull-up driver is driven by HV (high voltage), which improves the VOH (output high voltage) range and improves the linearity of the NMOS pull-up driver as overdrive gets higher. In addition, the NMOS pull-up driver size is reduced to meet the same VOH range, which improves area and pad capacitance.

[00019] Some embodiments of the disclosure comprise a pn-over-n device circuit to pology. The pn-over-n topology refers to a transistor stack with both P-type and N-type tran sistors in the upper stack coupled to the supply rail, and merely N-type transistors in the low er stack coupled to the ground. This circuit topology is unlike the n-over-n topology with de vice and resistor implementations. The n-over-n topology refers to a transistor stack with merely N-type transistors in the upper stack connected to the supply rail, and merely N-type transistor in the lower stack coupled to the ground. The pn-over-n device topology assists with lowering the pad parasitic capacitance. The pn-over-n device topology also helps with meeting target output voltage swing and slew rate specifications over a wide range of output stage supply voltage (e.g., from substantially 0.3 to substantially 0.7V), while offering an ex tremely area-efficient solution.

[00020] One or more embodiments are described with reference to the enclosed fig ures. While specific configurations and arrangements are depicted and discussed in detail, it should be understood that this is done for illustrative purposes only. Persons skilled in the relevant art will recognize that other configurations and arrangements are possible without departing from the spirit and scope of the description. It will be apparent to those skilled in the relevant art that techniques and/or arrangements described herein may be employed in a variety of other systems and applications other than what is described in detail herein.

[00021] Reference is made in the following detailed description to the accompanying drawings, which form a part hereof and illustrate exemplary embodiments. Further, it is to be understood that other embodiments may be utilized and structural and/or logical changes may be made without departing from the scope of claimed subject matter. It should also be noted that directions and references, for example, up, down, top, bottom, and so on, may be used merely to facilitate the description of features in the drawings. Therefore, the following de tailed description is not to be taken in a limiting sense and the scope of claimed subject mat ter is defined solely by the appended claims and their equivalents.

[00022] In the following description, numerous details are set forth. However, it will be apparent to one skilled in the art, that the present invention may be practiced without these specific details. In some instances, well-known methods and devices are shown in block dia gram form, rather than in detail, to avoid obscuring the present invention. Reference through out this specification to“an embodiment” or“one embodiment” or“some embodiments” means that a particular feature, structure, function, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the ap pearances of the phrase“in an embodiment” or“in one embodiment” or“some embodi ments” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, functions, or characteristics may be combined in any suitable manner in one or more embodiments. For example, a first embodiment may be combined with a second embodiment anywhere the par ticular features, structures, functions, or characteristics associated with the two embodiments are not mutually exclusive.

[00023] Note that in the corresponding drawings of the embodiments, signals are rep resented with lines. Some lines may be thicker, to indicate more constituent signal paths, and/or have arrows at one or more ends, to indicate primary information flow direction. Such indications are not intended to be limiting. Rather, the lines are used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit or a logical unit. Any represented signal, as dictated by design needs or preferences, may actually com prise one or more signals that may travel in either direction and may be implemented with any suitable type of signal scheme.

[00024] As used in the description and the appended claims, the singular forms“a”, “an” and“the” are intended to include the plural forms as well, unless the context clearly in dicates otherwise. It will also be understood that the term“and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[00025] The term“device” may generally refer to an apparatus according to the con text of the usage of that term. For example, a device may refer to a stack of layers or struc- tures, a single structure or layer, a connection of various structures having active and/or pas sive elements, etc. Generally, a device is a three-dimensional structure with a plane along the x-y direction and a height along the z direction of an x-y-z Cartesian coordinate system. The plane of the device may also be the plane of an apparatus which comprises the device.

[00026] The terms“coupled” and“connected,” along with their derivatives, may be used herein to describe functional or structural relationships between components. It should be understood that these terms are not intended as synonyms for each other. Rather, in partic ular embodiments,“connected” may be used to indicate that two or more elements are in di rect physical, optical, or electrical contact with each other.“Coupled” may be used to indicat ed that two or more elements are in either direct or indirect (with other intervening elements between them) physical or electrical contact with each other, and/or that the two or more el ements co-operate or interact with each other (e.g., as in a cause an effect relationship).

[00027] The terms“over,”“under,”“between,” and“on” as used herein refer to a rela tive position of one component or material with respect to other components or materials where such physical relationships are noteworthy. For example, in the context of materials, one material or material disposed over or under another may be directly in contact or may have one or more intervening materials. Moreover, one material disposed between two mate rials may be directly in contact with the two layers or may have one or more intervening lay ers. In contrast, a first material“on” a second material is in direct contact with that second material/material. Similar distinctions are to be made in the context of component assemblies.

[00028] Tire terms“left,”“right,”“front,”“back,”“top,� � and“bottom” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions.

[00029] The term“adjacent” here generally refers to a position of a thing being next to (e.g., immediately next to or close to with one or more things between them) or adjoining an other thing (e.g., abutting it).

[00030] The term "circuit" or“module” may refer to one or more passive and/or active components that are arranged to cooperate with one another to provide a desired function.

[00031] The term "signal" may refer to at least one current signal, voltage signal, mag netic signal, or data/clock signal. The meaning of "a," "an," and "the" include plural refer ences. The meaning of "in" includes "in" and "on."

[00032] The term“scaling” generally refers to converting a design (schematic and lay out) from one process technology to another process technology and subsequently being re duced in layout area. The term“scaling” generally also refers to downsizing layout and de- vices within the same technology node. The term“scaling” may also refer to adjusting (e.g., slowing down or speeding up - i.e. scaling down, or scaling up respectively) of a signal fre quency relative to another parameter, for example, power supply level. The terms“substan tially,”“close,”“approximately,”“near,” and“about,” generally refer to being within +/- 10% of a target value.

[00033] Unless otherwise specified the use of the ordinal adjectives“first,”“second,” and“third,” etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner.

[00034] As used throughout this description, and in the claims, a list of items joined by the term“at least one of’ or“one or more of’ can mean any combination of the listed terms. For example, the phrase“at least one of A, B or C” can mean A; B; C; A and B; A and C; B and C; or A, B and C.

[00035] The term“between” may be employed in the context of the z-axis, x-axis or y- axis of a device. A material that is between two other materials may be in contact with one or both of those materials, or it may be separated from both of the other two materials by one or more intervening materials. A material that is between two other materials may be in contact with one or both of those materials, or it may be separated from both of the other two materi als by one or more intervening materials, either temporally, spatially, in ranking or connected to one or both of those devices, or it may be separated from both of the other two devices by one or more intervening devices.

[00036] It is pointed out that those elements of the figures having the same reference numbers (or names) as the elements of any other figure can operate or function in any manner similar to that described, but are not limited to such.

[00037] FIG. 1 illustrates a schematic 100 of a Memory/Controller interface. Control ler interface 140 comprises a transmitter block, which includes: a Transmit circuitry 102, a Phase Locked Loop (PLL) and Clock Distribution circuity 104, a transmitter (TX) clock cir cuitry 106 (e.g., which comprises a Delay Locked Loop (DLL) and Phase Integrator (PI) TX). The controller 140 also comprises a receiver circuitry 114. FIG. 1 illustrates a Matched Re ceiver circuitry 114, comprising a Matched Filter 108, an Rx Clock recovery 110; and an RX receiver circuitry 112. The Rx Clock circuitry 110 extracts the clock signal from the received data stream through data output strobe DQS 130, and comprises a Voltage Controlled Delay Line (VCDL) and a Phase Integrator (PI). VCDL adds a van able amount of sample delay to its input signal. For example, the VCDL receives the data output strobe DQS 130, adjusts a phase of a sampling clock of the data output strobe DQS 130. The PI allows the Rx Clock recovery circuitry 110 to adjust the phase of the sampling clock in relatively fine increments. The Matched Filter 108 operates such that a delay on data output DQ 128 matches at least a minimum delay of data output strobe DQS 130. The RX receiver 112 extracts the data from the data stream output of the Matched Filter 108.

[00038] The Memory interface 150 comprises an RX receiver 120, which is coupled to a Clock Distributor 122. The Memory interface 150 also comprises Transmitters 124 and 126, which transmit data signals on lines data output (DQ) 128 and data output strobe (DQS) 130, respectively.

[00039] Although FIG. 1 illustrates an example, schematic 100 includes example im plementations of the controller interface 140 and the memory interface 150, any appropriate variations of the controller interface 140 and the memory interface 150 may be possible. Some embodiments of the present disclosure relate to the memory controller transmitter 102, although some other embodiments of the present disclosure may relate to any other appropri ate type of transmitter as well.

[00040] During previous generation of DDR technologies with higher I/O supply volt age (e.g. DDRl=2.5V, DDR2=l.8V, DDR3=l.5V, DDR4=l.2V, etc.), memory controller transmitters with PMOS pull-up and NMOS pull-down drivers were working well. However, with the next generation DDR technologies (e.g. LP4x, LP5, DDR5) with low I/O supply voltage (e.g., 0.3V) and the requirement of having combo transmitter supporting both DDR4 (1.2V) and LP4x, LP5, DDR5 (to 0.3V) with stacked thin gate transistors, the PMOS pull-up driver is running into operational issues with I/O supply voltage at 0.6V or lower. As I/O supply voltage goes down, source voltage of the pull-up PMOS driver goes down, so does overdrive voltage (e.g., V _gs - V _t ) and the PMOS transistors becomes non-functional specifi cally at slow process comer nodes.

[00041] FIG. 2 illustrates a schematic of a memory controller transmitter 200 (also referred to as transmitter 200, or a combo transmitter 200) with stacked p-over-n design, ac cording to some embodiments of the disclosure. The p-over-n design refers to a transistor stack with P-type transistors in the upper stack coupled to the supply rail, and N-type tran sistors in the lower stack connected to the ground. In some embodiments, the combo trans mitter 200 comprises a stacked p-over-n design. In some embodiments, the combo transmit ter 200 also comprises a stacked NMOS pull-up driver e.g., for low-swing applications. The combo transmitter 200 of various embodiments solves the low voltage functional issue (e.g. seen by current LP4x, DDR5, LP5, based drivers etc.) by having an NMOS at the pull-up coupled to a low voltage power supply.

[00042] Traditionally (e.g., for relatively higher values of supply voltage, such as at least as high as 1.0 V), P-type transistors are used for pull-up. This is because, for a relative ly low drive voltage, N-type pull-up transistors may not be fully switched on. Using an bi- type pull-up transistor may result in the voltage swing at the output node to be in the millivolt range, which is generally not sufficient for traditional transmitters·

[00043] However, as the supply voltage becomes relatively low (e.g., at 0.7 V, or even lower), an N-type pull-up transistor may be switched on during the pull-up operation. The N- type pull-up transistor may cause a voltage swing in the range of hundreds of millivolts (mV), e.g., in the range of about 150 mV to about 300 mV. Such a low voltage swing may be suffi cient for modern transmitters and receivers, such as transmitters and receivers used for newer generation memory like LP4x DDR, LP5 DDR, DDR5, etc.

[00044] Thus, for example, having an NMOS at the pull-up enables the combo trans mitter 200 to operate at a low voltage supply (e.g., lower than 0.7 V), which allows the com bo transmitter 200 to be used for low voltage memory applications, such as LP4x, LP5 mem ories, or other low voltage memory applications.

[00045] This low voltage driver supply (e.g., substantially 0.5V or lower) may be shared with a memory (e.g. DRAM) driver as well. For memory technologies using a higher voltage (e.g. substantially 1.2V for DDR4), a PMOS pull-up stack may be used.

[00046] In some embodiments, the memory controller transmitter 200 comprises a first power supply rail V _cc ; a second power supply rail V _cct , and a third power supply rail V _CCd. In some embodiments, the first power supply V _cc is higher than each of the second power supply V _cct and third power supply V _CCd · In some embodiments, the memory controller transmitter 200 comprises a DDR driver circuitry 202 coupled to the first power supply rail V _cc and the second power supply rail V _cct . In some embodiments, the memory controller transmitter 200 comprises a second LPDDR driver circuitry 204 coupled to the third power supply rail V _CCd .

[00047] In some embodiments, the LPDDR driver circuitry 204 is coupled to the first DDR driver circuitry 202 via a resistive device 206 (e.g., which may comprise a resistor, or any other appropriate resistive device). While in an example the resistive device 206 (or any other resistive device or resistor illustrated in other figures) can be a resistor, in other exam ples, the resistive device 206 may be a transistor operating in an active region, a passive resis tor offered by a process node (e.g., a poly resistor), a thin film resistor, devices made on front-end (e.g., active regions up to lower level metal layers such as Metal 3) of a die, devices made on a backend (upper level metal layers such as M4 and higher) of a die, off-chip resis tive device, on-die resistive device, resistive devices formed in a substrate of a package, and/or the like.

[00048] In some embodiments, the memory controller transmitter 200 comprises a stack of transistors of N conductivity type (NPui, NPu ₂ ), coupled to the first power supply rail V _co In some embodiments, the stack of transistors of N conductivity type (NPui, NPu ₂ ) is coupled to the LPDDR driver circuitry (junctions 208, and 220). In some embodiments, the stack of transistors comprises two N conductivity type transistors NPui, NPu ₂ . In some em bodiments, the input gate terminal of transistor NPui is coupled to an enable input (enp _u ), and the gate terminal of transistor NPu ₂ is coupled to the LPDDR driver circuitry (junction 208).

[00049] With the NMOS pull-up driver comprising n-type transistors NP _ui and NP _u2 of some embodiments, the output waveform at a pad (e.g., which is at an output of the transmit ter 200) is functional at I/O supply voltages all the way down to substantially 0.3 V, for ex ample. In some embodiments, having an NMOS in the pull-up driver makes the output at the pad less sensitive to the I/O supply voltage variations. As the source of the NMOS pull-up driver is connected to the pad and by looking at the source (pad) of a small signal model of a MOSFET, the pull-up path acts as constant current source (gmV _gs ). This current source is a strong function of V _gs and the pad voltage becomes a weak function of Vds (Rds). Therefore, the output high voltage VOH will be in the range of smaller V _ga - V _t and not greater than the I/O supply voltage. Furthermore, VOH is a strong function of V _gs - V _t and to improve the VOH, in some embodiments, the gate voltage is connected to high voltage (e.g., 1.2V) in stead of low voltage (e.g., 0.85V).

[00050] FIG. 3 illustrates a schematic of a DDR driver circuitry 300, according to some embodiments. In some embodiments, the DDR driver circuitry 300 corresponds to the DDR driver circuitry 202 of Fig. 2. In some embodiments, the DDR driver circuitry 300 comprises a first stack of transistors including a first transistor Pi _a (e.g., a p-type transistor) and a second transistor P ₂ (e.g., a p-type transistor) coupled in series, and having a first com mon node Yi. In some embodiments, the first transistor Pi _a is coupled to the first power sup ply rail V _cc In some embodiments, the DDR driver circuitry 300 comprises a third transistor Pi _b (e.g., a p-type transistor) coupled to the first common node Y i. In some embodiments, the third transistor P _2a is coupled to the second power supply rail V _cct ·

[00051] In some embodiments, the DDR driver circuitry 300 comprises a second stack of transistors of an opposite conductivity type to the first stack of transistors. In some embod iments, the second stack of transistors includes: a fourth transistor Ni (e.g., a n-type transis- tor) and a fifth transistor N _2a (e.g., an n-type transistor) coupled in series and having a second common node Y ₂ . In some embodiments, the second stack of transistors is coupled in series to the first stack of transistors and having a third common node Y _p . In some embodiments, the second stack of transistors comprises a sixth transistor Na _> (e.g., an n-type transistor) cou pled to the second common node Y ₂ , wherein the sixth transistor N _2b is coupled to the second power supply rail V _cct .

[00052] In some embodiments, a gate terminal of the transistor Pi _a is coupled to a data input (datai), and a gate terminal of the transistor P _2a is coupled to a first bias (pbias); and a gate terminal of the transistor P _2a is coupled to an enable input (enp _d ). In some embodiments, a gate terminal of the transistor Ni is coupled to a second bias (nbias), and a gate terminal of the transistor N _2a is coupled to a second data input (data ₂ ), and a gate terminal of the third n- type transistor Na is coupled to an enable input (enp _d ).

[00053] Referring to Figs. 2-3, in some embodiments, transistors NPul and NPu2 of Fig. 2 act as an NMOS pull-up circuitry, e.g., as discussed with respect to Fig. 2. Also, the transistors Ni, N _2a and Na of the DDR driver 202 (illustrated in Fig. 3) may act as a pull down circuitry for the transmitter 200.

[00054] FIG. 4 illustrates a schematic of a LPDDR driver circuitry 400, according to some embodiments. In some embodiments, the LPDDR driver circuitry 400 corresponds to the LPDDR driver circuitry 204 of Fig. 2. In some embodiments, the LPDDR driver circuitry 400 comprises a first stack of transistors including a p-type transistor P ₃ and a p-type transis tor P ₄ coupled in series and having a first common node Y ₃ . In some embodiments, the p- type transistor P ₃ is coupled to the third power supply rail V _CCd ·

[00055] In some embodiments, the LPDDR driver circuitry 400 comprises a second stack of transistors of an opposite conductivity type compared to the first stack of transistors. In some embodiments, the second stack of transistors includes: an n-type transistor N ₃ and an n-type transistor N _4a coupled in series and having a second common node Y ₄ . In some em bodiments, the second stack of transistors is coupled in series to the first stack of transistors and having a third common node Yo. In some embodiments, the second stack of transistors comprises an n type transistor N _4b coupled to the second common node Y ₄ . In some embodi ments, the n type transistor N _4b is coupled to the resistive device 206 via junction 220 (as shown in FIG. 2).

[00056] In some embodiments, a gate terminal of the transistor P ₃ is coupled to a data input (data ₃ ), and a gate terminal of the transistor P ₄ is coupled to a bias (pbias) . In some embodiments, a gate terminal of the transistor N ₃ is coupled to a bias (nbias), and a gate terminal of the transistor N ₄ is coupled to a data input (data ₄ ), and a gate terminal of the transistor N _4b is coupled to an enable input (enp _u ).

[00057] Referring to FIGs. 2-4, in some embodiments, the DDR driver 202 (e.g., see FIG. 3) provides a pull-up path using P-type transistors, and also provides a pull-down path using N-type transistors. The LPDDR driver 204 (e.g., see FIG. 3) provides a pull-up path using p-over-n stack of transistors. The NMOS pull-up circuitry (e.g., comprising transistors NP _ui and NP _U2 ) of FIG. 2 provides a pull-up path using N-type transistors.

[00058] The pull-up path to be used may be based on a type of memory with which the combo transmitter driver 200 is being used. For example, for relatively high voltage (e.g., greater than 1.0 V) memory (e.g., such as DDR1, DDR2, DDR3, DDR4, etc.), the pull-up path (e.g., using P-type transistors) and the pull-down path (e.g., using N-type transistors) of the DDR driver 202 may be used. Because P-type transistors are better suited for pull-up drivers when the input voltage is relatively high (e.g., higher than 1.0 V, for reasons dis cussed in further details herein), the pull-up path using the P-type transistors of the DDR driver 202 may be appropriately used.

[00059] On the other hand, for relatively low voltage (e.g., less than 0.7 V) memory (e.g., such as LP4x, LP5, etc.), the NMOS pull-up circuitry (e.g., comprising transistors NP _ui and NPU2 of FIG. 2) may be used, along with the pull-down path (e.g., using N-type transis tors) of the DDR driver 202. Because N-type transistors are better suited for pull-up drivers when the input voltage is relatively low (e.g., higher than 0.7 V, for reasons discussed in fur ther details herein), the pull-up path using the N-type transistors of the NMOS pull-up circuit ry of FIG. 2 may be appropriately used.

[00060] Thus, the combo transmitter 200 may be used for high voltage memory and/or low voltage memory, and hence, the name“combo” transmitter.

[00061] FIG. 5 illustrates a schematic of a common pull pre-driver 500, according to some embodiments. In some embodiments, the common pull pre-driver 500 comprises data input 502, Driver input 504, and Equalizer (EQ) input 506. In some embodiments, the data input 502, Driver input 504, and Equalizer (EQ) input 506 are coupled to Time to Clock Out (TCO)/Delay circuitries 508, 510 and 511, respectively. The common pull pre-driver 500 drives the combo transmitter 200 of FIGs. 2-4.

[00062] In some embodiments, since the combo transmitter driver 200 has both P and N Pull-up paths, a common pull-up pre-driver is used to support both paths. Pull-up pre driver 514 is designed in both High Voltage (HV) and Low Voltage (LV) power supply do mains and there are three outputs for each bit in the pull-up pre-driver. [00063] The pull-up pre-driver 514 outputs include: datai output corresponding to data input datai of FIG. 3 ); pbias output corresponding to pbias input of FIG. 3 and FIG. 4, enp _u output corresponding to enp _u input of FIG. 2 and FIG. ), and a datai output corresponding to data input datai of FIG. 4 ). PMOS pull-up pre-driver (514) is driven by the level shifted P_pup gated data from pre-driver logic (512) output (518). NMOS pull-up pre-driver (516) is driven by two outputs HV and LV (520) from pull-up pre-driver to drive the final full-swing inverter. These outputs are generated from N_pup gated data from pre-driver logic out (522) and both LV and HV outputs go through the level shifter to match delay between these out puts. The NMOS pull-up pre-driver 516 outputs include: data ₄ output corresponding to data input data4 of FIG. 4; and nbias output corresponding to nbias input of FIG. 4. The gated da ta (both p_up and n_up) from the pre-driver logic out are combined with impedance compen sation (RCOMP) code before getting applied to the driver. In addition, there is custom logic in the pre-driver to perform different functionalities, such as Equalizer (EQ) functionality. RCOMP code enables to compensate for process, temperature, and/or voltage variations in the termination impedance. Generally, a duplicate I/O buffer with a termination impedance is compared with a reference impedance to generate the RCOMP code. This RCOMP code is then supplied to other I/Os to bring their termination impedance characteristics to be similar to those of the duplicate I/O buffer.

[00064] In an example, since there is common NMOS Pull-down in the DDR driver 202 (e.g., as shown in FIG. 3), there may not be a difference in the pull-down pre-driver to support both DDR4 and LP4x/LP5 technologies. In some embodiments, the pull-down pre driver (524) is coupled to the Pre-driver logic 512 via link 526, and is designed in the LV power supply domain and the purpose of it is to feed the data to the gate of the NMOS pull down driver. The NMOS pull-down pre-driver 524 outputs include: datai output correspond ing to data input datai of FIG. 3; nbias output corresponding to nbias input of FIG. 3; and enp _d output corresponding to enp _d input of FIG. 3. In some embodiments, to match the delay between the pull-up and pull-down pre-drivers, buffers are added in the pull-down pre-driver 524. In some embodiments, if there is some variation in delay across PVT (process, voltage, and temperature) between the pull-up and pull-down electrical paths (which could cause duty cycle issues), e.g., during the post-Si, the Time-to-Clock output (TCO) training along with raised ground supply (Vsshi) is utilized to fix any mismatch. Vsshi (High Ground/VSS) is used to protect PFET devices from overstress by elevating the gate voltage to ground (e.g., elevating the Vgs by + 200mV). In some embodiments, the gated data from pre-driver logic out are combined with the RCOMP code before getting applied to the TX driver. Some other embodiments comprise custom logic in the pre-driver to perform different functionalities, such as Equalizer (EQ) functionality.

[00065] FIGs. 6A-6B illustrate two different transmitter output stage topologies. FIG. 6A illustrates a n-over-n topology 600a. The output stage comprises two N-type transistor Ni and N ₄ and two n-type cascode transistors N ₂ and N ₃ . FIG. 6B illustrates a p-over-n topology (600b), comprising of two input signal transistors Ni and P ₂ and two cascode transistors Pi and N _2.

[00066] The n-over-n transmit output stage of Fig. 6A uses increased predriver and driver supply voltages, when it is to provide higher output swing. The n-over-n topology also offers linearity and output voltage swing at low supply voltages (e.g., 0.3-0.4V), but suffers from maximum swing issue at higher supply voltages (e.g., 0.6-0.7V or higher). To increase the output swing in the n-over-n topology, the pre-driver supply voltage and output stage supply voltage are increased simultaneously, resulting in increased power dissipation in the pre-driver stage.

[00067] The p-over-n topology of Fig. 6B offers an alternative to n-over-n, but is lim ited by the pull-up slew rate. In some embodiments, a pn-over-n topology (discussed with respect to FIG. 7 herein below) addresses both the limited output swing issue with the n- over-n and the poor slew rate issue with the p-over-n topology by employing a p and n device combination in the pull-up driver branch.

[00068] FIG. 7 illustrates a pn-over-n transmitter output stage 700, according to some embodiments. In some embodiments, the pn-over-n topology of Fig. 7 addresses both the limited output swing issue with n-over-n and poor slew rate issue with p-over-n topology by employing a p+n device combination in the pull-up branch.

[00069] In some embodiments, the pn-over-n transmitter output stage 700 comprises a first stack of transistors including a first p-type transistor Pi and a second p-type transistor P ₂ coupled in series and having a first common node Yi. In some embodiments, the first p-type transistor Pi is coupled to a power supply rail Vddq. In some embodiments, the first stack of transistors is coupled to a second stack of transistors of an opposite conductivity type to the first stack of transistors. In some embodiments, the second stack of transistors comprises a third p-type transistor N3 and a fourth n-type transistor N ₄ coupled in series and having a sec ond common node Y ₂ . In some embodiment, the n-type transistor N3 is coupled to the power supply rail Vddq.

[00070] In some embodiments, the pn-over-n transmitter output stage 700 comprises a third stack of transistors of an opposite conductivity type coupled to the first stack of transis- tors. In some embodiments, the third stack of transistors includes: a fifth n-type transistor Ni and a sixth n-type transistor N2 coupled in series and having a third common node Y3. In some embodiments, the third stack of transistors is coupled in series to the first stack of tran sistors and having a fourth common node V _out , and a fifth common node D _. In some embod iments the first stack of transistors comprises a p-type transistor.

[00071] In some embodiments, a gate terminal of the first p-type transistor Pi is cou pled to a first enable input (enb), and a gate terminal of the second p-type transistor P ₂ is coupled to a first input data (D), and a gate terminal of the third n-type transistor N3 is cou pled to a second enable input (en), and a gate terminal of the fourth n-type transistor N ₄ is coupled to a second input data (D _t> ). In some embodiments, a gate terminal of the fifth n-type transistor Ni is coupled to the input data (D), and a gate terminal of the sixth n-type transistor N2 is coupled to the second enable input (en).

[00072] Referring to FIGs. 6A, 6B, and 7, the pn-over-n transmitter output stage 700 of Fig. 7 is a combination of the n-over-n topology 600a of Fig. 6A and the p-over-n topolo gy of Fig. 6B. In some embodiments, sections of the pn-over-n transmitter output stage 700 of Fig. 7 are selectively activated, e.g., based on a desired output voltage swing and a voltage level of the supply voltage.

[00073] For example, if a relatively low output voltage swing is desired and the supply voltage is relatively low, the output stage 700 is operated in a n-over-n topology (e.g., by ac tivating and using transistors Nl, N2, N3, and N4). Thus, from operational stand-point, the output stage 700 becomes similar to the n-over-n topology of FIG. 6A, and provides linearity and output voltage swing at relatively low supply voltages (e.g., 0.3-0.4V, less than 0.7 V, etc.).

[00074] On the other hand, for example, if a relatively high output voltage swing is desired and/or if the supply voltage is higher (e.g., 0.7 or higher), the output stage 700 is op erated in a p-over-n topology (e.g., by activating and using transistors Pl, P2, Nl, and N2). Thus, from operational stand-point, the output stage 700 becomes similar to the p-over-n to pology of FIG. 6B, and offers the higher voltage swing.

[00075] In yet another example, irrespective of the supply voltage (or at least for some supply voltage), both the pull-up paths (e.g., a first pull-up path comprising the P-type tran sistors Pl, P2, and a second pull-up path comprising the N-type transistors Nl, N2) of the output stage 700 may be operational, which provides the combined benefits of FIGs. 6A and 6B. [00076] FIG. 8A illustrates a test setup 800a for testing different output stage topolo gies. The set up 800a is used to test the pulse response of the three different output stage to pologies: n-n (600a), p-n (600b) and pn-n (700). FIG. 8B illustrates the pulse response out puts for n-n (600a), p-n (600b) and pn-n (700) topologies. The pulse response (e.g., 6.4Gb/s with 156.25 ps pulse width) simulation results for the three topologies under iso-loading, iso supply voltage conditions demonstrates the shortcomings of topologies of n-over-n (n-n) and p-over-n (p-n), and improvements offered by topology pn-over-n (pn-n).

[00077] Table 1 compares the performance of each topology based on sensitivity of swing and slew rate from the output stage supply voltage (V _ddq ) perspective.

Table 1

[00078] FIG. 9 illustrates post-layout simulation result of the pull-up (FIG. 9A) and pull-down (FIG. 9B) impedances of the output stage, implemented as a function of different number of legs (1-16) across three process corners (Pl, P2, and P3), according to some em bodiments. In memory cells, the PVT (process, voltage, and temperature) control circuit con sists on a PVT sensor block. The PVT control circuit is used to track the PVT conditions, and output driver block, which is split on several legs that are used for the adjustment of output driver impedance according to the detected PVT condition. The results demonstrate the capa- bility of the output stage to be tuned to a target 50W impedance accounting for PVT varia tions, without having to use device and resistor implementations. Implementing the output stage as device-only configuration reduces the pad parasitic capacitance, for example, by ap proximately 30%, thereby improving the bandwidth of the output node allowing scalability of the interface, for example, up to lOGb/s data rates.

[00079] FIG. 10 illustrates a system 1000 in which a mobile computing platform 1005 and/or a data server machine 1006 employs circuitry including at least one memory controller transmitter, for example in accordance with some embodiments described elsewhere here in. In some embodiments, the mobile computing platform 1005 and/or a data server machine 1006 may comprise transmitter 200 or combo transmitter 200, as discussed with respect to FIGs. 2-9. The server machine 1006 may be any commercial server, for example including any number of high-performance computing platforms disposed within a rack and networked together for electronic data processing, which in the exemplary embodiment includes a cir cuitry 1050. The mobile computing platform 1005 may be any portable device configured for each of electronic data display, electronic data processing, wireless electronic data transmis sion, or the like. For example, the mobile computing platform 1005 may be any of a tablet, a smart phone, laptop computer, etc., and may include a display screen (e.g., a capacitive, in ductive, resistive, or optical touchscreen), a chip-level or package-level integrated system 1010, and a battery 1015.

[00080] Whether disposed within the integrated system 1010 illustrated in the expand ed view 1020, or as a stand-alone discrete or packaged multi-chip module within the server machine 1006, the circuit includes at least one memory controller transmitter, for example in accordance with some embodiments described elsewhere herein. Circuitry 1050 may be fur ther attached to a board, a substrate, or an interposer 1060 along with a power management integrated circuit (PMIC). Functionally, PMIC 1030 may perform battery power regulation, DC-to-DC conversion, etc., and so has an input coupled to battery 1015 and with an output providing a current supply to other functional modules.

[00081] Circuitry 1050, in some embodiments, includes RF (wireless) integrated cir cuitry (RFIC) further including a wideband RF (wireless) transmitter and/or receiver (TX/RX including a digital baseband and an analog front end module comprising a power amplifier on a transmit path and a low noise amplifier on a receive path). The RFIC includes at least one memory controller transmitter device, for example in a memory controller transmitter circuit as describe elsewhere herein. The RFIC has an output coupled to an antenna (not shown) to implement any of a number of wireless standards or protocols, including but not limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolu tion (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any other wireless protocols that are desig nated as 3G, 4G, 5G, and beyond.

[00082] While certain features set forth herein have been described with reference to various implementations, this description is not intended to be construed in a limiting sense. Hence, various modifications of the implementations described herein, as well as other im plementations, which are apparent to persons skilled in the art to which the present disclosure pertains are deemed to lie within the spirit and scope of the present disclosure.

[00083] It will be recognized that the invention is not limited to the embodiments so described, but can be practiced with modification and alteration without departing from the scope of the appended claims. For example, the above embodiments may include specific combinations of features as further provided in examples below.

[00084] Fig. 11 illustrates a smart device or a computer system or a SoC (System-on- Chip) employing a dual power transmitter, according to some embodiments of the disclosure. It is pointed out that those elements of Fig. 11 having the same reference numbers (or names) as the elements of any other figure can operate or function in any manner similar to that de scribed, but are not limited to such.

[00085] Fig. 11 illustrates a block diagram of an embodiment of a computing device in which a dual power transmitter could be used, according to some embodiments. In some em bodiments, computing device 1600 represents a mobile computing device, such as a compu ting tablet, a mobile phone or smart-phone, a wireless-enabled e-reader, or other wireless mobile device. It will be understood that certain components are shown generally, and not all components of such a device are shown in computing device 1600.

[00086] In some embodiments, computing device 1600 includes first processor 1610 with a memory controller transmitter, according to some embodiments discussed. Other blocks of the computing device 1600 may also include transmitter 200, combo transmitter 200, according to some embodiments. The various embodiments of the present disclosure may also comprise a network interface within 1670 such as a wireless interface so that a sys tem embodiment may be incorporated into a wireless device, for example, cell phone or per sonal digital assistant.

[00087] In some embodiments, processor 1610 can include one or more physical de vices, such as microprocessors, application processors, microcontrollers, programmable logic devices, or other processing means. The processing operations performed by processor 1610 include the execution of an operating platform or operating system on which applications and/or device functions are executed. The processing operations include operations related to I/O (input/output) with a human user or with other devices, operations related to power man agement, and/or operations related to connecting the computing device 1600 to another de vice. The processing operations may also include operations related to audio I/O and/or dis play I/O.

[00088] In some embodiments, computing device 1600 includes audio subsystem 1620, which represents hardware (e.g., audio hardware and audio circuits) and software (e.g., drivers, codecs) components associated with providing audio functions to the computing de vice. Audio functions can include speaker and/or headphone output, as well as microphone input. Devices for such functions can be integrated into computing device 1600, or connected to the computing device 1600. In one embodiment, a user interacts with the computing device 1600 by providing audio commands that are received and processed by processor 1610.

[00089] In some embodiments, computing device 1600 comprises display subsystem 1630. Display subsystem 1630 represents hardware (e.g., display devices) and software (e.g., drivers) components that provide a visual and/or tactile display for a user to interact with the computing device 1600. Display subsystem 1630 includes display interface 1632, which in cludes the particular screen or hardware device used to provide a display to a user. In one embodiment, display interface 1632 includes logic separate from processor 1610 to perform at least some processing related to the display. In one embodiment, display subsystem 1630 includes a touch screen (or touch pad) device that provides both output and input to a user.

[00090] In some embodiments, computing device 1600 comprises I/O controller 1640. I/O controller 1640 represents hardware devices and software components related to interac tion with a user. I/O controller 1640 is operable to manage hardware that is part of audio sub system 1620 and/or display subsystem 1630. Additionally, I/O controller 1640 illustrates a connection point for additional devices that connect to computing device 1600 through which a user might interact with the system. For example, devices that can be attached to the com puting device 1600 might include microphone devices, speaker or stereo systems, video sys tems or other display devices, keyboard or keypad devices, or other I/O devices for use with specific applications such as card readers or other devices.

[00091] As mentioned above, I/O controller 1640 can interact with audio subsystem 1620 and/or display subsystem 1630. For example, input through a microphone or other au dio device can provide input or commands for one or more applications or functions of the computing device 1600. Additionally, audio output can be provided instead of, or in addition to display output. In another example, if display subsystem 1630 includes a touch screen, the display device also acts as an input device, which can be at least partially managed by I/O controller 1640. There can also be additional buttons or switches on the computing device 1600 to provide I/O functions managed by I/O controller 1640.

[00092] In some embodiments, I/O controller 1640 manages devices such as accel erometers, cameras, light sensors or other environmental sensors, or other hardware that can be included in the computing device 1600. The input can be part of direct user interaction, as well as providing environmental input to the system to influence its operations (such as filter ing for noise, adjusting displays for brightness detection, applying a flash for a camera, or other features).

[00093] In some embodiments, computing device 1600 includes power management 1650 that manages battery power usage, charging of the battery, and features related to power saving operation. Memory subsystem 1660 includes memory devices for storing information in computing device 1600. Memory can include nonvolatile (state does not change if power to the memory device is interrupted) and/or volatile (state is indeterminate if power to the memory device is interrupted) memory devices. Memory subsystem 1660 can store applica tion data, user data, music, photos, documents, or other data, as well as system data (whether long-term or temporary) related to the execution of the applications and functions of the computing device 1600.

[00094] Elements of embodiments are also provided as a machine-readable medium (e.g., memory 1660) for storing the computer-executable instructions (e.g., instructions to implement any other processes discussed herein). The machine-readable medium (e.g., memory 1660) may include, but is not limited to, flash memory, optical disks, CD-ROMs, DVD ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, phase change memory (PCM), or other types of machine-readable media suitable for storing electronic or computer- executable instructions. For example, embodiments of the disclosure may be downloaded as a computer program (e.g., BIOS) which may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals via a communication link (e.g., a modem or network connection).

[00095] In some embodiments, computing device 1600 comprises connectivity 1670. Connectivity 1670 includes hardware devices (e.g., wireless and/or wired connectors and communication hardware) and software components (e.g., drivers, protocol stacks) to enable the computing device 1600 to communicate with external devices. The computing device 1600 could be separate devices, such as other computing devices, wireless access points or base stations, as well as peripherals such as headsets, printers, or other devices.

[00096] Connectivity 1670 can include multiple different types of connectivity. To generalize, the computing device 1600 is illustrated with cellular connectivity 1672 and wire less connectivity 1674. Cellular connectivity 1672 refers generally to cellular network con nectivity provided by wireless carriers, such as provided via GSM (global system for mobile communications) or variations or derivatives, CDMA (code division multiple access) or vari ations or derivatives, TDM (time division multiplexing) or variations or derivatives, or other cellular service standards. Wireless connectivity (or wireless interface) 1674 refers to wire less connectivity that is not cellular, and can include personal area networks (such as Blue tooth, Near Field, etc.), local area networks (such as Wi-Fi), and/or wide area networks (such as WiMax), or other wireless communication.

[00097] In some embodiments, computing device 1600 comprises peripheral connec tions 1680. Peripheral connections 1680 include hardware interfaces and connectors, as well as software components (e.g., drivers, protocol stacks) to make peripheral connections. It will be understood that the computing device 1600 could both be a peripheral device ("to" 1682) to other computing devices, as well as have peripheral devices ("from" 1684) connected to it. The computing device 1600 commonly has a "docking" connector to connect to other compu ting devices for purposes such as managing (e.g., downloading and/or uploading, changing, synchronizing) content on computing device 1600. Additionally, a docking connector can allow computing device 1600 to connect to certain peripherals that allow the computing de vice 1600 to control content output, for example, to audiovisual or other systems.

[00098] In addition to a proprietary docking connector or other proprietary connection hardware, the computing device 1600 can make peripheral connections 1680 via common or standards-based connectors. Common types can include a Universal Serial Bus (USB) con nector (which can include any of a number of different hardware interfaces), DisplayPort in cluding MiniDisplayPort (MDP), High Definition Multimedia Interface (HDMI), Firewire, or other types.

[00099] Reference in the specification to "an embodiment," "one embodiment," "some embodiments," or "other embodiments" means that a particular feature, structure, or charac teristic described in connection with the embodiments is included in at least some embodi ments, but not necessarily all embodiments. The various appearances of "an embodiment," "one embodiment," or "some embodiments" are not necessarily all referring to the same em bodiments. If the specification states a component, feature, structure, or characteristic "may," "might," or "could" be included, that particular component, feature, structure, or characteris tic is not required to be included. If the specification or claim refers to "a" or "an" element, that does not mean there is only one of the elements. If the specification or claims refer to "an additional" element, that does not preclude there being more than one of the additional ele ment.

[000100] Furthermore, the particular features, structures, functions, or characteristics may be combined in any suitable manner in one or more embodiments. For example, a first embodiment may be combined with a second embodiment anywhere the particular features, structures, functions, or characteristics associated with the two embodiments are not mutually exclusive.

[000101] While the disclosure has been described in conjunction with specific embodi ments thereof, many alternatives, modifications and variations of such embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description. The embod iments of the disclosure are intended to embrace all such alternatives, modifications, and var iations as to fall within the broad scope of the appended claims.

[000102] In addition, well known power/ground connections to integrated circuit (IC) chips and other components may or may not be shown within the presented figures, for sim plicity of illustration and discussion, and so as not to obscure the disclosure. Further, ar rangements may be shown in block diagram form in order to avoid obscuring the disclosure, and also in view of the fact that specifics with respect to implementation of such block dia gram arrangements are highly dependent upon the platform within which the present disclo sure is to be implemented (i.e., such specifics should be well within purview of one skilled in the art). Where specific details (e.g., circuits) are set forth in order to describe example em bodiments of the disclosure, it should be apparent to one skilled in the art that the disclosure can be practiced without, or with variation of, these specific details. The description is thus to be regarded as illustrative instead of limiting.

[000103] The following examples pertain to further embodiments. Specifics in the ex amples may be used anywhere in one or more embodiments. All optional features of the ap paratus described herein may also be implemented with respect to a method or process.

[000104] Example 1. In one example, an apparatus is provided comprising: a first power supply rail to provide a first power supply; second and a third power supply rails to provide second and third power supplies, respectively, wherein a voltage level of the first power sup ply is higher than a voltage level of the second and third power supplies; a first driver circuit ry coupled to the first and second power supply rail; a second driver circuitry coupled to the third power supply rail, and coupled to the first driver circuitry; and a stack of transistors of N conductivity type coupled to the first power supply rail, and the second driver circuitry.

[000105] Example 2. The apparatus of Example 1, wherein the first driver circuitry comprises: a first stack of transistors of a P conductivity type comprising: a first transistor and a second transistor coupled in series and with a first common node, wherein the first tran sistor is coupled to the first power supply rail; and a third transistor coupled to the first com mon node, wherein the third transistor is coupled to the second power supply rail; and a sec ond stack of transistors of an N conductivity type coupled to the first stack of transistors, wherein the second stack of transistors comprises: a fourth transistor and a fifth transistor coupled in series and with a second common node, wherein the second stack of transistors is coupled in series to the first stack of transistors and wherein the first and second stack of transistors have a third common node that is coupled to the second driver circuitry; and a sixth transistor coupled to the second common node, wherein the sixth transistor is coupled to the second power supply rail.

[000106] Example 3. The apparatus of Examples 1-2, wherein the second driver circuit ry comprises: a third stack of transistors of the P conductivity type including a seventh tran sistor and an eight transistor coupled in series and with a fourth common node, wherein the seventh transistor is coupled to the third power supply rail; and a fourth stack of transistors of the N conductivity type coupled to the third stack of transistors, wherein the fourth stack of transistors comprises: a ninth transistor and a tenth transistor coupled in series and with a fifth common node, wherein the fourth stack of transistors is coupled in series to the third stack of transistors and has a sixth common node; and an eleventh transistor coupled to the sixth common node, wherein the eleventh transistor is coupled to a resistive device.

[000107] Example 4. The apparatus of Examples 1-3, wherein: a gate terminal of the first transistor is coupled to a data input; a gate terminal of the second transistor is coupled to a bias; and a gate terminal of the third transistor is coupled to an enable input.

[000108] Example 5. The apparatus of Examples 1-4, wherein: a gate terminal of the fourth transistor is coupled to a bias; a gate terminal of the fifth transistor is coupled to a data input; and a gate terminal of the third transistor is coupled to an enable input.

[000109] Example 6. The apparatus of Examples 1-5, wherein a gate terminal of the seventh transistor is coupled to a data input; and wherein a gate terminal of the eighth transis tor is coupled to a bias. [000110] Example 7. The apparatus of Examples 1-6, wherein a gate terminal of the ninth transistor is coupled to a data input; a gate terminal of the tenth transistor is coupled to a bias; and a gate terminal of the eleventh transistor is coupled to an enable input.

[000111] Example 8. The apparatus of Examples 1-7, wherein the first stack of transis tors comprises a p-type transistor.

[000112] Example 9. The apparatus of Examples 1-8, wherein the third stack of transis tors comprises a p-type transistor.

[000113] Example 10. The apparatus of Examples 1-9, wherein the stack of transistors of N conductivity type are coupled to the first driver circuitry via the resistive device.

[000114] Example 11. The apparatus of Examples 1-10, wherein the first driver circuit ry comprises a DDR driver circuitry, and the second driver circuitry comprises a LPDDR driver circuitry.

[000115] Example 12. In one example, a system is provided comprising: a memory to store instructions; a processor coupled to the memory and to execute the instructions, the pro cessor comprising: a first power supply rail to provide a first power supply; second and a third power supply rails to provide second and third power supplies, respectively, wherein a voltage level of the first power supply is higher than a voltage level of the second and third power supplies; a first driver circuitry coupled to the first and second power supply rail; a second driver circuitry coupled to the third power supply rail, and coupled to the first driver circuitry; and a stack of transistors of N conductivity type coupled to the first power supply rail, and the second driver circuitry; and a wireless interface to allow the processor to com municate with another system.

[000116] Example 13. The system of Example 12, wherein the first driver circuitry comprises: a first stack of transistors of a P conductivity type comprising: a first transistor and a second transistor coupled in series and with a first common node, wherein the first tran sistor is coupled to the first power supply rail; and a third transistor coupled to the first com mon node, wherein the third transistor is coupled to the second power supply rail; and a sec ond stack of transistors of an N conductivity type coupled to the first stack of transistors, wherein the second stack of transistors comprises: a fourth transistor and a fifth transistor coupled in series and with a second common node, wherein the second stack of transistors is coupled in series to the first stack of transistors and wherein the first and second stack of transistors have a third common node that is coupled to the second driver circuitry; and a sixth transistor coupled to the second common node, wherein the sixth transistor is coupled to the second power supply rail. [000117] Example 14. The system of Examples 12-13, wherein the second driver cir cuitry comprises: a third stack of transistors of the P conductivity type including a seventh transistor and an eight transistor coupled in series and with a fourth common node, wherein the seventh transistor is coupled to the third power supply rail; and a fourth stack of transis tors of the N conductivity type coupled to the third stack of transistors, wherein the fourth stack of transistors comprises: a ninth transistor and a tenth transistor coupled in series and with a fifth common node, wherein the fourth stack of transistors is coupled in series to the third stack of transistors and has a sixth common node; and an eleventh transistor coupled to the sixth common node, wherein the eleventh transistor is coupled to a resistive device.

[000118] Example 15. The system of Examples 12-14, wherein: a gate terminal of the first transistor is coupled to a data input; a gate terminal of the second transistor is coupled to a bias; and a gate terminal of the third transistor is coupled to an enable input.

[000119] Example 16. The system of Examples 12-15, wherein: a gate terminal of the fourth transistor is coupled to a bias; a gate terminal of the fifth transistor is coupled to a data input; and a gate terminal of the third transistor is coupled to an enable input.

[000120] Example 17. The system of Examples 12-16, wherein a gate terminal of the seventh transistor is coupled to a data input; and wherein a gate terminal of the eighth transis tor is coupled to a bias.

[000121] Example 18. The system of Examples 12-17, wherein a gate terminal of the ninth transistor is coupled to a data input; a gate terminal of the tenth transistor is coupled to a bias; and a gate terminal of the eleventh transistor is coupled to an enable input.

[000122] Example 19. The system of Examples 12-18, wherein the stack of transistors of N conductivity type are coupled to the first driver circuitry via the resistive device.

[000123] Example 20. The system of Examples 12-19, wherein the first driver circuitry comprises a DDR driver circuitry, and the second driver circuitry comprises a LPDDR driver circuitry.

[000124] Example 21. In one example, an apparatus is provided comprising: a power supply rail to provide a power supply; a first stack of transistors including: a first transistor and a second transistor coupled in series and having a first common node, wherein the first transistor is coupled to the first power supply rail; and a second stack of transistors of an op posite conductivity type to the first stack of transistors, wherein the second stack of transis tors includes: a third transistor and a fourth transistor coupled in series and with a second common node, wherein the third transistor is coupled to the power supply rail. [000125] Example 22. The apparatus of Example 21, comprising a third stack of transis tors of an opposite conductivity type to the first stack of transistors, wherein the third stack of transistors comprises: a fifth transistor and a sixth transistor coupled in series and with a third common node, wherein the third stack of transistors is coupled in series to the first stack of transistors and with fourth and fifth common nodes.

[000126] However, the above embodiments are not limited in this regard and, in various implementations, the above embodiments may include the undertaking only a subset of such features, undertaking a different order of such features, undertaking a different combination of such features, and/or undertaking additional features than those features explicitly listed. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.