DESCRIPTION

The invention relates to a method for making the comparison between a continuous value analogue signal and a continuous value digital signal.

The invention also relates to a circuit architecture configured to carry out the aforesaid method of the invention.

The project leading to this application has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 653355.

It is known that information within the fields of electronics and informatics may be represented mainly in two ways: by means of analogue type signals or by means of numerical or digital type signals. The information content with the first is represented by the values that the physical signal may take on, and therefore it continuously varies within the dynamics of the signal.

The information content in the case of digital signals instead is again represented by the values that the physical signal may take on, but in this case the significant values are a finite set.

It is just as known that in the various implementations of electronic or informatics systems, there is the need to process such signals in order to interpret and/or modify the contents thereof. With regard to processing analogue signals, more specifically, it provides directly acting on the physical signal. Therefore here, the processing processes continuous-time and continuous-value signals.

The processing of digital type signals instead provides acting on the information extracted from the physical signal transporting it.

The digital (or numerical) processing of the signal therefore intrinsically processes discrete-time and discrete-value signals.

The analogue processing limits of the analogue signals consist in having to build circuits capable of directly acting on the analogue signals themselves. A further limit of this type of processing is due to the presence of the intrinsic noise in the analogue signal or caused by the analogue processing circuit built to process the signal itself. Such problems have encouraged operators to develop techniques for representing the information and for processing which are immune or less sensible thereto. This has resulted in the tendency to convert the analogue signals into digital signals capable of being processed by electronic computers. However, the limit of such conversion consists in the fact that inevitably the digital signal obtained from a corresponding analogue signal has less information than the latter.

Having made such premises of general nature, it is known that there is the need in certain applications to compare an analogue type signal with a digital type signal, the latter representing for example a threshold value.

While considering what is said above, in order to compare such two signals which are different in nature, the background art tends to convert the analogue signal into a digital signal, to then compare them by means of a digital processing system.

The background art possibly also provides carrying out the conversion in opposite direction, and that is to convert the digital signal into a corresponding analogue signal, and then to compare them by means of a conveniently built analogue circuit system.

Both such approaches have certain drawbacks, especially if such comparison is to be implemented by minimizing the voltage consumption, the use of integrated electronic components and, accordingly, the space in which to make such processing circuit.

Such needs are highly felt, for example, in the case of an electronic circuit for processing digital images to be made on the same silicon substrate in which the pixel array of the sensor is defined.

Indeed, both such approaches firstly require the conversion of one of the two signals into the form of representation of the second.

Moreover, if the comparison of two analogue type signals is to be made, as mentioned above, it requires the definition of an analogue type electronic circuit, which naturally has high voltage consumption. Furthermore, again disadvantageously, if the second signal is a threshold, such analogue approach does not allow modifying the value thereof in an easy and quick manner.

The comparison made in purely digital manner also requires making an integrated circuit with a non-negligible number of transistors and therefore with the significant use of the silicon surface.

The present invention intends overcoming all the drawbacks mentioned.

In particular, the object of the invention is to define a method and propose a circuit architecture for making the comparison between a continuous value analogue signal and a continuous value digital signal which allows having a smaller voltage consumption with respect to a method and relative comparison circuit of the purely analogue type.

It is a further object of the invention to define a method and propose a relative circuit architecture which allow ensuring increased flexibility in selecting and varying the value of the second signal - for example a threshold value - to be compared with the first signal, with respect to a method and a related comparison circuit of purely analogue type.

It is also an object of the invention to define a method and propose a circuit architecture which allow reducing the number of integrated electronic components required for the implementation thereof with respect to a method and a relative comparison circuit of purely digital type.

Accordingly, the object of the invention is to define a method and propose a circuit architecture which allow reducing the silicone area occupied with respect to a method and a relative comparison circuit of the purely digital type. The aforesaid objects are achieved by the method of the invention for making the comparison between a continuous value analogue signal and a continuous value digital signal having the features according to independent claim 1 .

Such objects are also achieved by the circuit architecture configured to carry out the aforesaid method of the invention, having the features according to claim 8.

Further features of the method and of the circuit architecture of the invention are described in the dependent claims.

The aforesaid objects, together with the advantages described below, will be noted during the description of certain preferred implementation embodiments of the invention, which are given by way of non-limiting indicative example, with reference to the accompanying drawings, where:

- figures 1 a and 1 b depict time diagrams of the signals involved in carrying out the method of the invention according to the preferred implementation embodiment, respectively in the case in which the analogue signal S1 has a greater value than the digital signal S2 and in the case in which the analogue signal S1 has a lesser value than the digital signal S2;

- figures 2a and 2b depict time diagrams of the signals involved in carrying out the method of the invention according to an alternative implementation embodiment, respectively in the case in which the analogue signal S1 has a greater value than the digital signal S2 and in the case in which the analogue signal S1 has a lesser value than the digital signal S2;

- figure 3 diagrammatically depicts the circuit architecture of the invention, configured to carry out the method of the invention.

To clarify the execution of the method of the invention, which is adapted to compare a continuous value analogue signal S1 and a continuous value digital signal S2, certain time diagrams relative to the signals considered in the various execution steps of the method itself are introduced and taken into consideration below. In particular, the time diagrams in figures 1 a and 1 b depict the signals involved in carrying out the method of the invention according to a preferred implementation embodiment thereof, while the time diagrams in figures 2a and 2b depict the signals considered during the execution of the method of the invention according to an alternative implementation embodiment thereof.

Furthermore, it is to be noted that figures 1 a and 2a hypothesize the execution of the method of the invention with the analogue signal S1 having a greater value with respect to the value of the digital signal S2. Figures 1 b and 2b instead hypothesize the opposite situation, that is in the case in which the analogue signal S1 has a lesser value with respect to the value of the digital signal S2.

Again, for the aforesaid preferred implementation embodiment, as well as for the alternative implementation embodiment, the analogue signals considered are voltage signals. However, it is not excluded for the analogue signals to be current signals in further implementation embodiments alternative to the ones above.

Starting now to describe the execution of the method of the invention according to the preferred implementation embodiment, it provides defining a ramp analogue signal RAMP having linearly variable value over time. As noted in figures 1 a and 1 b, such ramp analogue signal RAMP in particular is of the type which increases linearly over time.

Such definition of the ramp analogue signal RAMP requires periodically varying, for each time interval belonging to first predetermined time intervals ck1 , a first digital numerical value cntl by a predetermined quantity, and also providing to convert such first digital numerical value cntl into the aforesaid ramp analogue signal RAMP by means of a digital/analogue converter.

More specifically, according to the preferred implementation embodiment of the invention, the ramp analogue signal RAMP of the linearly increasing type is obtained by increasing the first digital numerical value cntl - preferably initialized at the value "0" - by such predefined quantity, which usually is selected equal to one unit.

Alternatively, according to the alternative implementation embodiment in figures 2a and 2b, the ramp analogue signal RAMP is defined so that it is a linearly decreasing ramp analogue signal. Such a decreasing trend is obtained by decreasing the aforesaid first digital numerical value cntl initialized at a predefined positive value, by such predefined quantity, which preferably is selected equal to one unit. Here too there is a need, for each first time interval ck1 , to convert the first digital numerical value cntl by means of the aforesaid digital/analogue converter in order to obtain such decreasing ramp analogue signal RAMP.

Whether or not according to the preferred implementation embodiment or according to the alternative implementation embodiment, the method of the invention also provides simultaneously comparing the value of the ramp analogue signal RAMP with the analogue signal S1 and the first digital numerical value cntl with the digital signal S2 at each of such first predetermined time intervals ck1.

Such a comparison therefore allows the method of the invention to verify at which of the first predetermined time intervals ck1 the value of the ramp analogue signal RAMP equals the analogue signal S1 and at which of the same predetermined time intervals ck1 the first digital numerical value cntl equals the digital signal S2. Accordingly, the method of the invention is capable of temporally defining which of the aforesaid equalities occurs first and which occurs second, and is also capable of defining the time window WIND between the first equality and the second equality.

Considering now the four time diagrams introduced above, it is worth noting for figure 1 a - which provides an increase of the first digital numerical value cntl and accordingly, a linear increase of the ramp analogue signal RAMP - that the execution of the method of the invention allows identifying the equality of the digital signal S2 with such first digital numerical value cntl at a time interval ck1 prior to the time interval ck1 in which the equality occurs between the analogue signal S1 and the ramp analogue signal RAMP. The exact opposite occurs in figure 1 b, that is the execution of the method of the invention allows identifying the equality between the analogue signal S1 and the ramp analogue signal RAMP before the equality between the digital signal S2 with such first digital numerical value cntl .

With regard to figure 2a which, as mentioned above, depicts the alternative implementation embodiment of the method of the invention with the first digital numerical value cntl of decreasing type and accordingly the ramp analogue signal RAMP of increasing type, it is worth noting that the execution of the same method allows first identifying the equality between the analogue signal S1 and the ramp analogue signal RAMP and then the equality between the digital signal S2 with such first digital numerical value cntl .

Finally, for the case shown in figure 2b, the execution of the method of the invention allows first identifying the equality of the digital signal S2 with the first digital numerical value cntl and then the equality between the analogue signal S1 and the ramp analogue signal RAMP.

According to the preferred implementation embodiment of the method of the invention, the comparison operation at each of the first predetermined time intervals ck1 of the value of the ramp analogue signal RAMP with the analogue signal S1 consists in inputting the aforesaid two analogue signals into an analogue comparator, and it provides commuting, in output, a first output signal LS1 from a first value to a second value at the time interval ck1 in which the value of the ramp analogue signal RAMP equals the analogue signal S1. The method of the invention further provides keeping such first output signal LS1 constant at the aforesaid second value following such commutation.

Note the trend of the signal LS1 in figure 1 a and in figure 1 b for increased clarity.

As noted in figures 2a and 2b, also the alternative implementation embodiment provides carrying out the same comparison method and treating the first output signal LS1 in the same way as the preferred implementation embodiment described above. With regard to the comparison operation of the first digital numerical value cntl with the digital signal S2, the method according to the preferred implementation embodiment of the invention provides comparing each bit representing the first digital numerical value cntl with the bit in the same position representing the digital signal S2, at each of the predetermined time intervals ck1. Such comparison further provides commuting a second output signal LS2 from a first value to a second value at the time interval ck1 in which all the bits of the first digital numerical value cntl equal the corresponding bits of the digital signal S2, and keeping the second output signal LS2 constant at such second value following such commutation. Refer to the depiction of the signal LS2 in figures 1 a and 1 b for increased clarity.

As noted in figures 2a and 2b, also the alternative implementation embodiment of the method of the invention provides carrying out the same comparison method and treating the second output signal LS2 in the same way as that provided by the preferred implementation embodiment.

With regard to the step of defining the time order of the aforesaid equalities, it provides comparing the first output signal LS1 and the second output signal LS2 and establishing which of the two output signs LS1 and LS2 commutes first.

Moreover, the method of the invention provides defining a time window WIND between the moment in time ck1 in which the first of the aforesaid commutations occurs and the moment in time in which the second commutation occurs.

As noted in figures 1 a and 1 b for the preferred implementation embodiment of the invention and in figures 2a and 2b for the alternative implementation embodiment, the method provides increasing, during the aforesaid time window WIND, a second digital numerical value cnt2, preferably initialized at "0" before the beginning of the same time window WIND. Such an increase in particular occurs within the aforesaid time window WIND for each time interval belonging to second predetermined time intervals ck2. The duration of each time interval belonging to the aforesaid second predetermined time intervals ck2 could be equal to or less than the duration of each time interval belonging to the first predetermined time intervals ck1.

With regard to the meaning of the aforesaid second digital numerical value cnt2, it represents the deviation that exists between the analogue signal S1 and the digital signal S2.

In particular, such second digital numerical value cnt2 is increased during the time window WIND and at the closing of the latter the same second digital numerical value cnt2 represents the final deviation value between the analogue signal S1 and the digital signal S2.

Finally, the method of the invention provides the further step - always performed at each of the aforesaid second time intervals ck2 - of comparing the second digital numerical value cnt2 with a predetermined threshold value DELTA so as to verify if and when the same second digital numerical value cnt2 equals the predetermined threshold DELTA.

More specifically, the comparison operation of the second digital numerical value cnt2 with a predetermined threshold digital value DELTA at each of the second predetermined time intervals ck2 according to the preferred implementation embodiment of the invention provides comparing each bit representing the second digital numerical value cnt2 with the bit in the same position, which represents the predetermined threshold digital value DELTA. Moreover, the method of the invention provides commuting a third output signal SET from a first value to a second value at the time interval belonging to the second predetermined time intervals ck2 in which all the bits of the second digital numerical value cnt2 equal the corresponding bits of the predetermined threshold digital value DELTA and keeping the third output signal SET constant at the second value following such commutation.

Therefore, it is possible, with the method of the invention, to compare two signals S1 and S2 which are different in nature, in particular an analogue signal S1 and a digital signal S2.

An implementation embodiment of circuit architecture 1 depicted diagrammatically in figure 3 is now introduced; it is configured to carry out the comparison method of the invention between a continuous value analogue signal S1 and a continuous value digital signal S2.

In particular as noted in figure 3, such circuit architecture 1 comprises a first binary counter 2 configured to generate and periodically vary at first predetermined time intervals ck1 of the aforesaid first digital numerical value cntl .

Preferably, such first binary counter 2 uses one byte (8 bits) to define the aforesaid first digital numerical value cntl . The circuit architecture 1 also comprises a digital/analogue converter 3 operatively connected at the output of the first binary counter 2 so that the same digital/analogue converter 3 generates, in output, the ramp analogue signal RAMP having linearly variable value over time starting from such first digital numerical value cntl .

Advantageously, such first binary counter 2 and the relative digital/analogue converter 3 could already be present and used for other logic functions performed in the chip in which the aforesaid circuit architecture 1 of the invention is implemented. In other words, the implementation of the circuit architecture 1 of the invention advantageously could take advantage of the common circuit components usually present and used for multiple functions, thus avoiding to make the latter specifically.

As observed in figure 3, the circuit architecture 1 also comprises a first logical comparison group 4 configured to make the comparison between the value of the ramp analogue signal RAMP with the analogue signal S1 and to verify at which of the first predetermined time intervals ck1 the analogue signals S1 and RAMP equal one other.

According to the preferred implementation embodiment of the invention, the first logical comparison group 4 in particular comprises an analogue comparator 41 with a first input 41a connected to the digital/analogue converter 3 to receive, in input, the ramp analogue signal RAMP, and with a second input 41 b configured to receive, in input, the analogue signal S1. A first electronic storage circuit 42 is operatively connected downstream of such analogue comparator 41.

In particular, such first electronic storage circuit 42 is operatively connected with its input 42a to the output 41 c of the analogue comparator 41.

The first electronic storage circuit 42 according to the invention is configured to commute the first output signal LS1 from a first value to a second value at the time interval ck1 in which the analogue comparator 41 detects the equality between the value of the ramp analogue signal RAMP and the analogue signal S1. Moreover, such first electronic storage circuit 42 is configured to keep the first output signal LS1 constant at the aforesaid second value following such commutation.

As noted in figure 3, the first electronic storage circuit 42 is provided with an output 42b for making available the aforesaid first output signal LS1. The circuit architecture 1 of the invention also comprises a second logical comparison group 5 configured to make the comparison between the first digital numerical value cntl and the digital signal S2, and to verify at which of the first predetermined time intervals ck1 the digital signals S2 and cntl equal one other.

In particular, the second logical comparison group 5 comprises a number of logic gates 51 of "XNOR" type equal to the number of bits with which the first digital numerical value cntl and the digital signal S2 are defined. According to the preferred embodiment of the circuit architecture 1 of the invention, there are eight of such logic gates 51 of "XNOR" type, like the number of bits with which the first digital numerical value cntl and the digital signal S2 are represented.

Each of the aforesaid "XNOR" logic gates 51 is configured to receive, in input, bits having same position as the first digital numerical value cntl and the digital signal S2. Moreover, the totality of the "XNOR" logic gates 51 have their own outputs arranged at the input of a logical block 52 of "AND" type so as to obtain, at the output 52a of such logical block 52 of "AND" type, a logical value "1 " at the time interval ck1 in which all the bits of the first digital numerical value cntl equal the corresponding bits of the digital signal S2. Obviously, also such logical block 52 of "AND" type belongs to the second logical comparison group 5.

Moreover, the same second logical comparison group 5 comprises a second electronic storage circuit 53 operatively connected with its input 53a to the output 52a of the logical block 52 of "AND" type.

The second electronic storage circuit 53 in particular is configured to commute the aforesaid second output signal LS2 from a first value to a second value when the output 52a of the logical block 52 of "AND" type is equal to "1 ". The same second electronic storage circuit 53 is configured to keep the second output signal LS2 constant at such second value following the aforesaid commutation.

As noted in figure 3, the second electronic storage circuit 53 is provided with an output 53b for making available the second output signal LS2.

The circuit architecture 1 of the invention comprises also a third logical comparison group 6 configured to temporally define which of the two aforesaid equalities occurs first and which occurs second, and to define, further, the aforesaid time window WIND between the first equality and the second equality.

In particular, according to the preferred implementation embodiment of the invention, the third logical comparison group 6 comprises a first logic gate 61 of "AND" type configured to receive, in input, the first output signal LS1 and the negated of the second output signal LS2N and a second logic gate 62 of "AND" type configured to receive, in input, the negated of the same first output signal LS1 N and the second output signal LS2.

Moreover, the third logical comparison group 6 comprises a logic gate 63 of "OR" type configured to receive, in input, the outputs of the first logic gate 61 of "AND" type and of the second logic gate 62 of "AND" type so as to obtain the logical value "1 " on its output 63a for a time period that defines the time window WIND.

Finally, the third logical comparison group 6 comprises a third storage circuit 64 operatively connected with its input 64a, with the output exclusively of one between the first logic gate 61 of "AND" type and the second logic gate 62 of "AND" type. Such third storage circuit 64 is configured to commute its output 64b from a first value to a second value and to keep such output constant to the aforesaid second value in the case in which it receives, in input, the logical value "1 " from the logic gate of "AND" type to which it is connected.

In other words, the aforesaid third storage circuit 64 is configured to establish the sign of what was defined above as deviation between the analogue signal S1 and the digital signal S2.

Finally, the circuit architecture 1 of the invention provides a fourth logical comparison group 7 comprising a second binary counter 71 configured to generate and periodically vary the aforesaid second digital numerical value cnt2 at second predetermined time intervals ck2 during the time window WIND.

Such fourth logical comparison group 7 is configured to compare the second digital numerical value cnt2 with a predetermined threshold value DELTA at each of the aforesaid second time intervals ck2 so as to verify if and when the same second digital numerical value cnt2 equals the aforesaid predetermined threshold DELTA.

In detail, such second binary counter 71 is connected with its enabling input 71a with the output 63a of the logic gate 63 of "OR" type of the third logical comparison group 6 so that the same second binary counter 71 generates and periodically varies the value of the second digital numerical value cnt2 exclusively during the aforesaid time window WIND.

Furthermore, with regard to the fourth logical comparison group 7, it comprises a number of logic gates 72 of "XNOR" type equal to the number of bits with which the second digital numerical value cnt2 and the predetermined threshold value DELTA are defined.

Preferably, there are eight of the aforesaid logic gates 72 of "XNOR" type, as there are bits with which the second digital numerical value cnt2 and the predetermined threshold value DELTA are defined.

Each of the "XNOR" logic gates 72 is configured to receive, in input, the bit of the same position as the second digital numerical value cnt2 and as the predetermined threshold value DELTA. In their totality, such "XNOR" logic gates 72 have their outputs arranged in input at a logical block 73 of "AND" type so as to obtain, in output 73a from the same logical block 73 of "AND" type, a logical value "1 " at the time interval belonging to the aforesaid second predetermined time intervals ck2 in which all the bits of the second digital numerical value cnt2 equal the corresponding bits of the predetermined threshold value DELTA.

Clearly, the fourth logical comparison group 7 also comprises the aforesaid logical block 73 of "AND" type. Moreover, the fourth logical comparison group 7 comprises a fourth electronic storage circuit 74 operatively connected with its input 74a to the output 73a of the same logical block 73 of "AND" type.

According to the invention, such fourth electronic storage circuit 74 is configured to commute the third output signal SET from a first value to a second value when the output 73a of the logical block 73 of "AND" type is equal to "1 ". Furthermore, the fourth electronic storage circuit 74 is configured to keep such third output signal SET constant at the aforesaid second value following such commutation.

Finally, the fourth electronic storage circuit 74 according to the invention is provided with an output 74b so as to make such third output signal SET available to the outside for further processing.

Based on what is said, therefore, the method of the invention and the circuit architecture of the invention achieve all the preset objects.

In particular, the object is achieved of defining a method and proposing a circuit architecture for making the comparison between a continuous value analogue signal and a continuous value digital signal which allow having a smaller voltage consumption with respect to a method and a relative comparison circuit of the purely analogue type.

The object is also achieved of defining a method and proposing a relative circuit architecture which allow ensuring increased flexibility in selecting and varying the value of the second signal - for example a threshold value - to be compared with the first signal, with respect to a method and a related comparison circuit of purely analogue type.

The further object is achieved of defining a method and proposing a circuit architecture which allow reducing the number of integrated electronic components required for the implementation thereof with respect to a method and a relative comparison circuit of purely digital type.

Accordingly, the object was also achieved of defining a method and proposing a circuit architecture which allow reducing the silicone area occupied with respect to a method and a relative comparison circuit of the purely digital type.