Abstract:
An integrated circuit includes a first storage location, a first generator, a converter, and a second generator. The first storage location is operable to store a first adjustment value. The first generator is coupled to the first storage location, is operable to generate a first signal having a first characteristic, and includes a first adjuster operable to change the first characteristic in response to the first adjustment value. The converter is coupled to the first storage location and is operable to generate from the first adjustment value a modified adjustment value. The second generator is coupled to the converter, is operable to generate a second signal having a second characteristic, and includes a second adjuster operable to change the second characteristic in response to the modified adjustment value.

Description:
PRIORITY CLAIM 
     The present application claims the benefit of European Patent Application No. EP06117967.7, filed Jul. 27, 2006, which application is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     An embodiment of the present invention relates to the electronics field. More specifically, an embodiment of the invention relates to the trimming of electronic devices. 
     BACKGROUND 
     Producing electronic devices—and especially Integrated Circuits (ICs)—is a very complex task, which involves several phases. In general terms, starting from an IC architectural design, the required electronic circuit blocks are designed and simulated by means of CAD tools; then, a physical layout of several different IC layers is defined, and corresponding photolithographic masks (necessary for the planar technology manufacturing process) are fabricated. Once the masks are released, prototypes of the IC are created, and a testing phase is carried out to check whether the IC correctly performs the intended tasks and satisfies the design requirements. 
     However, during the actual manufacturing of the IC, there are a number of functional parameters (voltages, currents, time delays, resistance and capacitance values) that, despite careful design and simulation, are subjected to variations of their actual values with respect to the intended, expected ones. This is mainly due to the practical and, in some respects even theoretical, impossibility of eliminating fluctuations in several parameters of the manufacturing process (e.g., dopant species concentrations, alignment of masks, and a number of other variables). 
     As a consequence to these unavoidable, statistical variations in their functional parameters, several of the manufactured ICs may have to be discarded because they do not respect the intended specifications. 
     In order to avoid this, which could severely impact the manufacturing process yield, IC designers usually provide trimming structures in the ICs, being adapted to implement a post-manufacturing correction of at least the most critical functional parameters. 
     Several ways are possible for implementing the trimming process of these functional parameters, such as the provision of fuses to be selectively burnt. A more usual and preferred way calls for providing (trimming) configuration registers, usually programmable electrically and capable of retaining information even in absence of power supply. By storing prescribed configuration codes in these registers, different operating configurations for selected circuit blocks can be achieved, so as to correct the desired functional parameters at will. 
     Typically, this kind of trimming process is performed during the testing phase of the IC, and it can be expediently exploited not only for ensuring that a specific IC satisfies the desired requirements, but also as investigation means; in this way, IC designers and process engineers can refine the design and the process flow with the aim at coming to a consolidated product. 
     However, the trimming process described above is quite time consuming, since it requires measuring and accordingly correcting each functional parameter of interest individually. Moreover, the measuring of specific functional parameters may be difficult, if not impossible; for example, when a functional parameter is not directly available outside the IC it is necessary to provide additional circuitry dedicated to this purpose (which additional circuitry increases the size and the complexity of the whole IC). 
     A solution for alleviating the above-described drawbacks in a very specific situation is disclosed in the European Patent Application EP 1591858. Particularly, this document relates to the trimming of reference-voltage generators (for example, of the band-gap type). In this case, the above-described measuring and correcting operations are applied to a single reference-voltage generator only; the other reference-voltage generators are corrected in a proportional way (exploiting the fact that the fluctuations in the manufacturing process affect all the reference-voltage generators in a similar way). In this way, the trimming process of the reference-voltage generators is simplified. 
     However, the proposed solution is not of general applicability. Particularly, this technique does not solve the problem of measuring other functional parameters; as mentioned above, this problem is particular acute when the functional parameters are not directly available outside the IC. 
     Moreover, the document EP 1591858 does not cope with the additional problem of trimming the functional parameters with different accuracy. Indeed, in the solution disclosed in this document to each correction applied to the (measured) reference voltage corresponds a proportional correction for each other (non-measured) reference voltage; as a consequence, all the reference voltage generators are always trimmed in the same way. Therefore, it is not possible to discriminate functional parameters requiring different trimming processes (for example, because their accuracy is more or less critical for the operation of the IC). 
     SUMMARY 
     In its general terms, an embodiment of the present invention is based on the idea of implementing a many-to-one mapping of the corrections. 
     More specifically, an embodiment of the invention provides an electronic device; the electronic device has a plurality of operative parameters. The electronic device includes means for applying a plurality of trimming actions to each parameter (for causing a corresponding correction of the parameter). For at least one reference parameter, means is provided for measuring the reference parameter responsive to the application of the trimming actions (or a part thereof), in order to select one of the trimming actions that provides a target value of the reference parameter. Further means is used for forcing the application of the selected trimming action for the reference parameter. For each non-reference parameter—different from the reference parameter(s)—means is provided for selecting one of the trimming actions for the non-reference parameter corresponding to the selected trimming action for the reference parameter(s); the selection is performed according to a predetermined mapping of each group of multiple corrections of the reference parameter(s) on a single correction of the non-reference parameter. The electronic device further includes means for forcing the application of the selected trimming action for each non-reference parameter. 
     In an embodiment of the invention, a code—indicative of the corresponding selected trimming action—is stored for each reference parameter; the code(s) is/are then converted into another code being indicative of the selected trimming action for each non-reference parameter. 
     In an embodiment of the invention, a single reference parameter is used. 
     In this case, the mapping is based on a predefined relationship between the corrections for the reference parameter and the corrections for the non-reference parameter. 
     In another embodiment of the invention, multiple reference parameters are used. 
     In this case, the mapping is instead defined by combining the corrections for the reference parameters according to another relationship with the corrections for the non-reference parameter. 
     In one or more embodiments of the invention, the relationship is preferably linear. 
     Typically, the trimming action for each non-reference parameter is determined by approximation. 
     A suggested choice for the reference parameter(s) consists of a characteristic of a clock signal of the electronic device (such as its period). 
     It may be that the non-reference parameters cannot be measured from outside the electronic device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more embodiments of the invention, as well as further features and the advantages thereof, will be best understood with reference to the following detailed description, given purely by way of a non-restrictive indication, to be read in conjunction with the accompanying drawings, in which: 
         FIG. 1A  shows the functional blocks of a trimming structure known in the art, 
         FIG. 1B  illustrates an exemplary trimming table that can be used in the structure of  FIG. 1A , 
         FIG. 2  shows the functional blocks of a trimming structure according to an embodiment of the present invention, 
         FIG. 3A  illustrates a further exemplary trimming table that can be used in the structure of  FIG. 2  according to an embodiment of the invention, 
         FIG. 3B  is a diagram representing an exemplary relationship between two different functional parameters to be trimmed according to an embodiment of the invention, 
         FIG. 3C  illustrates an exemplary mapping between the two functional parameters of  FIG. 3B  according to an embodiment of the invention, 
         FIG. 4A  illustrates a still further exemplary trimming table that can be used in the structure of  FIG. 2  according to an embodiment of the invention, 
         FIG. 4B  is a diagram representing another exemplary relationship between two different functional parameters to be trimmed according to an embodiment of the invention, 
         FIG. 4C  illustrates an exemplary mapping between the two functional parameters of  FIG. 4B  according to an embodiment of the invention, 
         FIG. 5A  shows the functional blocks of a trimming structure according to a further embodiment of the present invention, 
         FIG. 5B  illustrates exemplary trimming tables for three different functional parameters that can be used in the structure of  FIG. 5A  according to an embodiment of the invention, and 
         FIG. 5C  is a matrix representing an exemplary mapping between the three functional parameters of  FIG. 5B  according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     With reference in particular to  FIG. 1A , the functional blocks of a trimming structure  100  known in the art are schematically shown. The trimming structure  100  is adapted to adjust a plurality of functional parameters of a generic IC, identified as  105 . 
     The IC  105  includes a core circuit  110  whose functioning (not relevant to the present discussion) requires a plurality of operative signals S(i); for the sake of simplicity,  FIG. 1A  illustrates two operative signals only, generically identified as S(i) and S(i+1). Each operative signal S(i) is directly generated inside the IC  105  (i.e., on-chip) by means of a respective operative generator RG(i). For example, the operative signals S(i) are clock signals, and the operative generators RG(i) are clock generator circuits. 
     Each operative signal S(i) is characterized by one or more functional parameters that may be subjected to variations of their actual values with respect to the expected ones. In the following, for the sake of simplicity, the operative signal and the corresponding functional parameter are identified with the same reference S(i). In case of clock signals, the durations of their clock periods might be considered critical functional parameters for the correct functioning of the IC  105 . 
     In order to tune the functional parameters S(i) to counterbalance the variations and obtain the desired expected values, each operative generator RG(i) includes a trimming circuit TC(i). The trimming circuit TC(i) is capable of adjusting the functional parameter S(i) in response to a trimming word TR(i); particularly, each value of the trimming word TR(i) k  (k=−N/2+1 to N/2) defines a different trimming action TA(i) k —implemented by the trimming circuit TC(i)—which typically causes a corresponding correction of the functional parameter S(i). 
     With reference to the specific case of the clock signals, and without descending into circuital details not relevant to the present discussion, each trimming circuit TC(i) includes a delaying element for regulating the clock period, like an RC network. Each RC network includes a resistor R(i), whose resistance can be trimmed in order to vary the clock period of the operative signal S(i). For example, the resistor R(i) includes a plurality of auxiliary resistors r(i)&lt;j&gt; (j=0 to M−1) that are selectively connectable in parallel to a main resistor B(i) by means of respective controlled switches SW(i)&lt;j&gt;; each controlled switch SW(i)&lt;j&gt; is selectively activatable by means of a corresponding digital trimming signal TR(i)&lt;j&gt;. Thus, by connecting a selected number of auxiliary resistors r(i)&lt;j&gt; in parallel to the main resistor B(i), the overall resistance of the resistor R(i) can be varied, and thus the clock period of the clock signal S(i) can be adjusted accordingly. The open/closed configuration of the switches SW(i)&lt;j&gt; is determined by the value assumed by the M trimming signals TR(i)&lt;j&gt;, which define as a whole the corresponding (M-bit) trimming word TR(i). 
     The operative signals S(i) are provided outside the IC  105  to a measuring circuit  120 , which is adapted to measure the functional parameters thereof (e.g., the clock periods of the clock signals) in such a way to make the results of the measurements available to an operator. Moreover, the measuring circuit  120  is capable of driving each trimming circuit TC(i) individually by setting a configuration code VC(i), which represents a corresponding trimming word TR(i); for example, the configuration code VC(i) includes a word of log 2 (M) bits. Each configuration code VC(i) is provided to the corresponding operative generator RG(i) and is converted into the trimming word TR(i) by a decoder D(i) included therein. 
     Each configuration code VC(i) can also be permanently stored in the IC  105  by means of a corresponding configuration register M(i), for example, a Read Only Memory (ROM). For this purpose, each configuration register M(i) has an input for receiving the desired configuration code VC(i), and an output for providing it to the corresponding operative generator RG(i). 
     In the following, an exemplary trimming process making use of the known trimming structure  100  of  FIG. 1A  will be described. For this purpose, each functional parameter S(i) is subjected to a dedicated “measuring and correcting” procedure. 
     However, before describing the procedure, it is necessary to illustrate a number of preliminary operations that must be carried out before the manufacturing of the IC  105 , i.e., during the IC architectural design. 
     More particularly, once established the expected value that the functional parameter S(i) has to assume ideally, the first preliminary operation includes defining a correction range thereof (for example, centered around the expected value); this is useful for dimensioning the trimming circuit TC(i), such as the resistor R(i) in the example at issue. The amplitude of the correction range depends on the expected variations of the functional parameter S(i) due to the tolerance of the manufacturing process used for integrating the IC  105 : the more mature the process, the narrower the correction range. 
     The next preliminary operation includes defining the resolution of the trimming circuit TC(i). With the term “resolution” it is intended the number of allowed corrections (N) for the functional parameter S(i) within the above defined correction range, wherein each correction is caused by a corresponding trimming action TA(i) k . In the example at issue, the resolution of the trimming circuit TC(i) depends on the number of auxiliary resistors r(i)&lt;j&gt; that can be connected in parallel to the main resistor B(i). The higher the number of auxiliary resistors r(i)&lt;j&gt;, the finer the overall resistance of the resistor R(i) can be varied, so that the finer the functional parameter S(i) can be trimmed. The amplitude of the resolution depends on the requested accuracy of the functional parameter S(i)—for example, due to its criticality for the correct operation of the IC  105 : the more accurate the functional parameter S(i), the higher the resolution. 
     The last preliminary operation includes associating a trimming word TR(i) k —represented by the corresponding configuration code VC(i) k —with each trimming action TA(i) k  for obtaining the desired correction of the functional parameter S(i). 
       FIG. 1B  shows an exemplary trimming table  130  including the results obtained by performing the above-mentioned preliminary operations. 
     According to this example, the correction range of the functional parameter S(i)—in this case, the clock period of the clock signal—is expressed as a percentage, and it extends from −28% to +32% with respect to the desired expected value (corresponding to a correction of 0%). The trimming table  130  includes 16 rows, each one corresponding to a particular trimming action TA(i) k , so that the resolution of the trimming circuit TC(i) is N=16. Assuming a constant difference between each pair of corrections caused by adjacent trimming actions TA(i) k —for example, when all the auxiliary resistors r(i)&lt;j&gt; have the same resistance—the correction range is equally subdivided in 16 parts. In this way, the resolution of the trimming circuit TC(i) expressed as a percentage, equal to the correction range divided by the number N of allowable corrections, is (32−(−28))/16≈4%. In this case, a possible coding of the 16=2 4  different trimming actions TA(i) k  makes use of a 4-bit configuration code VC(i), from “0111” (corresponding to k=−7) to “1111” (corresponding to k=+8) for corrections of corresponding sign. The trimming table  130  illustrates the association, with the configuration code VC(i) equal to VC(i) 0  corresponding to the 0% variation (i.e., corresponding to the expected value). 
     Once the preliminary operations have been performed, the measuring and correcting procedure is started. For this purpose, the measuring circuit  120  generates the configuration code VC(i), sweeping all the N possible values VC(i) k  thereof in succession, and provides it to the corresponding operative generator RG(i). In this way, the configuration code VC(i) k  is converted into the trimming word TR(i) k  by the decoder D(i) included therein; the trimming word TR(i) k  forces the trimming action TA(i) k , so as to apply the corresponding correction to the functional parameter S(i). The operative signal S(i) is then returned to the measuring circuit  120 , so as to measure the actual value reached by its functional parameter in response to the trimming action TA(i) k . 
     More particularly, at the beginning of the measuring and correcting procedure, the measuring circuit  120  sets the configuration code VC(i) to the value VC(i) 0  (i.e., corresponding to the 0% variation with respect the expected value). If the measured functional parameter S(i) does not correspond to the expected value (due to the tolerances of the manufacturing process used for integrating the IC  105 ), the measuring circuit  120  changes the configuration code VC(i), setting it to another value among those indicated in the trimming table  130 , until the expected value is reached (with an acceptable accuracy). Particularly, if the functional parameter S(i) has been ascertained to be higher than the expected value, the measuring circuit  120  reacts by driving the trimming circuit TC(i) so as to lower it (i.e., so as to obtain a negative correction thereof); if instead the functional parameter has been ascertained to be lower than the expected value, the measuring circuit  120  reacts by driving the trimming circuit TC(i) so as to increase it (i.e., so as to obtain a positive correction thereof). 
     Once the expected value has been reached, the configuration code VC(i) k  corresponding to the trimming action TA(i) k  that has produced the correction capable of counterbalancing the variation of the functional parameter S(i)—due to the tolerances of the manufacturing process—is stored into the configuration register M(i). 
     All the above-mentioned operations—that is, the preliminary operations for creating the trimming table and the measuring and correcting procedure—are repeated for all the functional parameters S(i) that are reputed to be significant for the correct functioning of the core circuit of the IC. In this way, after all the functional parameters S(i) have been trimmed, each configuration register M(i) stores a corresponding configuration code VC(i) k . The trimming actions TA(i) k  corresponding to the stored configuration codes VC(i) k  then remain the same during all the operative life of the IC  105 . 
     Turning now to  FIG. 2 , the functional blocks of a trimming structure  200  according to an embodiment of the present invention are schematically shown. The elements of the trimming structure  200  corresponding to the ones shown in the  FIG. 1A  are denoted with the same references, and their explanation is omitted for the sake of brevity. 
     In principle, the proposed trimming structure takes advantage of the fact that all the circuit blocks included in the IC  105  are subjected to steps of a same manufacturing process. In this way, the variations in all the functional parameters to be trimmed are in some way correlated to each other. Therefore, once the above-described trimming and correcting procedure has been accomplished for a subset of chosen functional parameters (from now on identified as “reference” parameters), it is possible to infer the trimming actions needed for correcting the other (non-reference) functional parameters, wherein the inference is based on predetermined relationships relating the effects of the fluctuations in the manufacturing parameters for the reference parameters to the ones for the non-references parameters. 
     As described in detail in the following, a solution according to an embodiment of the present invention maps groups of multiple corrections for the reference parameters onto a corresponding single correction for each non-reference parameter (either by aggregating the different corrections of a single reference parameter or by combining more reference parameters). 
     An embodiment is of general applicability. Particularly, this technique may avoid measuring whatever functional parameters; this advantage is clearly perceived when these functional parameters are not directly available outside the IC. 
     More specifically, to an embodiment of the invention allows trimming the functional parameters with different accuracy. Therefore, it is possible to discriminate functional parameters requiring different trimming processes (for example, because their accuracy is more or less critical for the operation of the IC). 
     Particularly, in an embodiment of the invention a single reference signal, denoted with S(r), is chosen. The reference parameter S(r) chosen may be the most critical one for the functioning of the core circuit  110  and/or as the one that can be measured in the easiest way; for example, a choice may be selecting the clock period of the most accurate clock signal in the IC  105 . 
     In this case, the measuring circuit  120  only receives the reference signal S(r) among the plurality of operative signals that are provided to the core circuit  110 . Furthermore, the trimming structure  200  only includes one configuration register, i.e., the configuration register M(r) corresponding to the reference signal S(r). 
     Regarding instead the other non-reference signals— FIG. 2  illustrates one of the non-reference signals only, generically identified as S(o)—the trimming structure  200  includes a converter CV(o) for each one of them. The converter CV(o) has an input terminal connected to the output terminal of the configuration register M(r)—for receiving the stored configuration code VC(r) associated with the reference signal S(r)—and an output terminal connected to the corresponding operative generator RG(o)—for providing the configuration code VC(o) forcing the desired trimming action on the non-reference parameter S(o). As it will be more clear in the following, the configuration code VC(o) is obtained from the configuration code VC(r) according to a relationship relating the corrections of the reference parameter S(r) with the corrections of the non-reference parameter S(o), which relationship is implemented by means of the converter CV(o). 
     Therefore, the above-described measuring and correcting procedure is performed for the reference parameter S(r) only; as above, the configuration code VC(r) k —corresponding to the trimming action TA(r) k  that has produced the correction capable of counterbalancing the variation of the reference parameter S(r)—is stored into the configuration register M(r). During the operative life of the IC  105 , the configuration code VC(r) k  is provided directly to the corresponding trimming circuit TC(r), whereas the same configuration code VC(r) k  is decoded into each other configuration code VC(o) p —through the converter CV(o)—which is in turn provided to the corresponding trimming circuit TC(o), so as to force the trimming actions causing the desired corrections of all the (reference and non-reference) functional parameters. 
     For the sake of conciseness, it is assumed that the reference signal S(r) is associated with the same trimming table  130  described with reference to the  FIG. 1B .  FIG. 3A  instead shows a further exemplary trimming table  330  regarding the non-reference parameter S(o)—for example, the clock period of another clock signal being less critical for the functioning of the IC  105 . The trimming circuit associated with the non-reference parameter S(o) likewise includes a resistor R(o) with variable resistance—having a structure that is similar to the resistor R(i) previously described, but with a lower number of auxiliary resistors r(o)&lt;j&gt;. 
     According to this example, the correction range of the non-reference parameter S(o) extends from −30% to +40% with respect to the desired expected value corresponding to a variation of 0%. The trimming table  330  includes P=8 rows, each one corresponding to a particular trimming action TA(o) p  (p=−P/2+1 to P/2). The resolution of the trimming circuit TC(o) expressed as a percentage is then equal to (40−(−30))/8=10%. In this case, a possible coding of the 8=2 3  different variations makes use of a 3-bit configuration code VC(o). The trimming table  330  illustrates the association, with the configuration code VC(o) equal to VC(o) 0  corresponding to the 0% variation. 
     In order to explain how the converter is capable of obtaining the configuration code VC(o) from the configuration code VC(r), reference will be now made to  FIG. 3B . 
     More particularly, this figure illustrates a diagram  350  representing the relationship between all the possible corrections of the reference parameter S(r) (to counterbalance corresponding variations caused by the fluctuations of the manufacturing process) and all the possible corrections of the non-reference parameter S(o) (to counterbalance corresponding variations caused by the same fluctuations of the manufacturing process). The diagram  350  has an abscissa axis, representing the corrections of the reference parameter S(r), and an ordinate axis, representing the corrections of the non-reference parameter S(o). In the example at issue, i.e., with both the reference parameter S(r) and the non-reference parameter S(o) that are clock periods, the relationship is linear, and is represented by a straight line  355 . This means that any variation of the reference parameter S(r) produces a proportional variation for the non-reference parameter S(o)—typically, substantially the same. In other words, if the reference parameter S(r) experiences a certain variation (for example, +10%), a corresponding, substantially similar +10% variation is experienced by the non-reference parameter S(o) as well. 
     The abscissa axis specifies all the possible 16 corrections that may be applied to the reference parameter S(r)—caused by the trimming actions TA(r) k  forced by the different values of the configuration code VC(r) k ; likewise, the ordinate axis specifies all the possible 8 corrections that may be applied to the non-reference parameter S(o)—caused by the trimming actions TA(o) p  forced by the different values of the configuration code VC(o) p . 
     The operation of the converter associated with the non-reference parameter S(o) consists of receiving the value of the configuration code VC(r) k  stored in the configuration register of the reference parameter S(r)—as chosen beforehand through the measuring and correcting procedure—and converting it into the value of the configuration code VC(o) p  that better approximates the value corresponding to the configuration code VC(r) k  according to the above-described relationship. More in detail, starting from the correction caused by the configuration code VC(r) k , a corresponding intermediate (or correction) value—denoted with IV(o)—is determined on the line  355 ; this intermediate value IV(o) represents the (ideal) correction that should have to be applied to the non-reference parameter S(o). The intermediate value IV(o) is then approximated to the closest (actual) correction that is available for the non-reference parameter S(o). The configuration code VC(o) p  causing the correction is then matched with the configuration code VC(r) k . 
     For example, if the configuration code for the reference parameter S(r) is VC(r) −2 =“0010”—corresponding to a correction of −8% triggered by the trimming action TA(r) −2 —the configuration code selected by the converter CV(o) for the non-reference parameter S(o) is VC(o) −1 =“001”—-corresponding to a correction of −10% triggered by the trimming action TA(o) −1 . 
       FIG. 3C  illustrates the resulting mapping of the corrections of the configuration code VC(r)—in the trimming table  130  of FIG.  1 B—on the corrections of the configuration code VC(o)—in the trimming table  330  of  FIG. 3A . As can be seen, since in the example at issue the resolution of the reference parameter S(r) is higher than that of the non-reference parameter S(o)—i.e., 16 and 8, respectively—each group of (in this case, two) adjacent configuration codes VC(r) k , VC(r) k+1  for the reference parameter S(r) is mapped on a single configuration code VC(o) p  for the non-reference parameter S(o). 
     In another application of the above-described embodiment, the non-reference parameter S(o) is a delay period generated by a delay line. An exemplary trimming table  430  regarding the non-reference parameter S(o) is illustrated in  FIG. 4A . 
     According to this further example, the correction range of the non-reference parameter S(o) extends from −25% to +25% with respect to the desired expected value corresponding to a variation of 0%. The trimming table  430  includes 3 rows, each one corresponding to a particular trimming action TA(o) p  (p=−1 to 1). The resolution of the trimming circuit TC(o) expressed as a percentage is now equal to (25−(−25))/3≈18%. In this case, a possible coding of the 3 different corrections makes use of a 2-bit configuration code VC(o). The trimming table  430  illustrates the association, with the configuration code VC(o) equal to VC(o) 0  corresponding to the 0% variation. 
     In order to explain how the converter is capable of obtaining the configuration code VC(o) from the configuration code VC(r), reference will be now made to  FIG. 4B . 
     More particularly, this figure illustrates a diagram  450  again representing the relationship between all the possible corrections of the reference parameter S(r) and all the possible corrections of the non-reference parameter S(o). However, in the example at issue wherein the reference parameter S(r) is a clock period and the non-reference parameter S(o) is a delay period, the relationship is now non-linear, and it is represented by a curve  455 . As above, the abscissa axis specifies all the possible 16 corrections that may be applied to the reference parameter S(r), whereas the ordinate axis now specifies all the possible 3 corrections that may be applied to the non-reference parameter S(o). 
       FIG. 4C  illustrates the resulting mapping of the corrections of the configuration code VC(r)—in the trimming table  130  of FIG.  1 B—on the corrections of the configuration code VC(o)—in the trimming table  430  of  FIG. 4A . As can be seen, a group of 8 configuration codes (from VC(r) −3  to VC(r) +4 ) is mapped on the configuration code VC(o) 0 , while two groups of 4 configuration codes (one including the configurations codes from VC(r) −7  to VC(r) −4  and one including the configurations codes from VC(r) 5  to VC(r) 8 ) are mapped on the configuration codes VC(o) −1  and VC(o) +1 , respectively. 
     Referring now to  FIG. 5A , the functional blocks of a trimming structure  500  according to an embodiment of the present invention are schematically shown. The elements of the trimming structure  500  corresponding to the ones shown in the  FIGS. 1A and 2  are denoted with the same references, and their explanation is omitted for the sake of brevity. 
     More particularly, according to this embodiment of the invention a pair of reference signals, denoted with S(r 1 ) and S(r 2 ), are chosen (for example, consisting of two different clock signals). In this case, the measuring circuit  120  receives the two reference signals S(r 1 ) and S(r 2 ) among the plurality of operative signals that are provided to the core circuit  110 . Furthermore, the trimming structure  500  now includes two configuration registers, i.e., the configuration register M(r 1 ) corresponding to the reference signal S(r 1 ) and the configuration register M(r 2 ) corresponding to the reference signal S(r 2 ). 
     Regarding instead the other non-reference signals— FIG. 5  illustrates one of the non-reference signals only, generically identified as S(o)—the trimming structure  500  again includes a converter CV′(o) for each one of them. However, in this case the converter CV′(o) has a first input terminal connected to the output terminal of the configuration register M(r 1 )—for receiving the stored configuration code VC(r 1 ) associated with the reference signal S(r 1 )—and a second input terminal connected to the output terminal of the configuration register M(r 2 )—for receiving the stored configuration code VC(r 2 ) associated with the reference signal S(r 2 ); as above, the converter CV′(o) as an output terminal connected to the corresponding operative generator RG(o)—for providing the configuration code VC(o) forcing the desired trimming action on the non-reference parameter S(o). The configuration code VC(o) is likewise obtained from the configuration codes VC(r 1 ) and VC(r 2 ) according to a relationship relating the corrections of the reference parameters S(r 1 ) and S(r 2 ) with the corrections of the non-reference parameter S(o), which relationship is implemented by means of the converter CV′(o). 
       FIG. 5B  illustrates two exemplary trimming tables  510 ,  520  of the reference parameters S(r 1 ), S(r 2 ) and an exemplary trimming table  530  of the non-reference parameter S(o). For the sake of conciseness, the trimming tables are not described in detail, being similar to those described above. Each generic row of the trimming tables  510 ,  520 ,  530  indicates a trimming action TA(r 1 ) k1 , TA(r 2 ) k2 , TA(o) p  corresponding to a configuration code VC(r 1 ) k1 , VC(r 2 ) k2 , VC(o) p , respectively. 
     In order to explain how the converter is capable of obtaining the configuration code VC(o) from the configuration codes VC(r 1 ) and VC(r 2 ), reference will be now made to  FIG. 5C . 
     More particularly,  FIG. 5C  shows a matrix  555  representing the mapping of the corrections of the configuration codes VC(r 1 ), VC(r 2 )—in the trimming tables  510 ,  520 —on the corrections of the configuration code VC(o)—in the trimming table  530 ; more in detail, the matrix  555  associates each pair of possible values of the configuration codes VC(r 1 ) k1 , VC(r 2 ) k2  with a possible value of the configuration codes VC(o) p . 
     The operation of the converter associated with the non-reference parameter S(o) includes receiving the value of the configuration codes VC(r 1 ) k1  and VC(r 2 ) k2  stored in the configuration registers of the reference parameters S(r 1 ) and S(r 2 ), respectively—as chosen beforehand through the measuring and correcting procedure—and converting them into the value of the configuration code VC(o) p  that better approximates the value corresponding to the pair of configuration codes VC(r 1 ) k1 , VC(r 2 ) k2  according to a predefined relationship. More in detail, an intermediate value is determined by combining the corrections caused by the configuration codes VC(r 1 ) k1  and VC(r 2 ) k2 —for example, as their average; this intermediate value represents the (ideal) correction that should have to be applied to the non-reference parameter S(o). The intermediate value is then approximated to the closest (actual) correction that is available for the non-reference parameter S(o). The configuration code VC(o) p  causing the correction is then matched with the pair of configuration codes VC(r 1 ) k1 , VC(r 2 ) k2 . 
     The above-described embodiment of the invention allows modeling whatever relationships between two (or more) reference parameters and each non-reference parameter; this allows taking into account more factors that may impact any functional parameter of the IC. 
     Moreover, the same technique may be advantageously exploited to increase the accuracy of the proposed solution; for example, it is possible to determine the trimming action for every non-reference parameter according to trimming actions applied to multiple reference parameters of the same type (such as clock periods), so as to reduce the effects of any inaccuracy in the corresponding mapping. 
     Naturally, in order to satisfy local and specific requirements, a person skilled in the art may apply to the embodiments described above many modifications and alterations. Particularly, although the present invention has been described with a certain degree of particularity with reference to embodiments thereof, it should be understood that various omissions, substitutions and changes in the form and details as well as other embodiments are possible; moreover, it is expressly intended that specific elements and/or method steps described in connection with any disclosed embodiment of the invention may be incorporated in any other embodiment as a general matter of design choice. 
     For example, similar considerations apply if the electronic device has a different structure or includes equivalent components. Moreover, although the proposed solution has been specifically designed for ICs, nothing prevents its application to any other type of electronic devices (for example, multi-chip packages). Of course, the examples described above (i.e., the operative signals, their functional parameters, the numerical values of the correction ranges, resolutions, corrections, trimming words and/or configuration codes) are merely illustrative. In any case, similar considerations apply to equivalent measuring and correcting procedures (for example, always involving the application of all the possible trimming actions for each reference parameter). Likewise, any other structure may be used to force the application of the desired trimming action (for example, by working at the level of the trimming words directly, without any configuration code). 
     The choice of generating the configuration codes for the non-reference parameters starting from the one being stored for the reference parameter(s) allows exploiting advantages of embodiments of the invention at their best; however, an embodiment of the invention also includes an implementation wherein the same technique is used only to avoid repeating the measuring operations for the non-reference parameters—i.e., calculating the corresponding configurations codes from the ones for the reference parameter(s) and then storing these values in respective configuration registers as usual. 
     Moreover, nothing prevents applying an embodiment to reference and non-reference parameters having the same resolution. 
     It is emphasized that the above-described relationships are not comprehensive; for example, the mapping may be based on a linear relationship being decreasing, on a quadratic relationship, on a logarithmic relationship, and so on. 
     Alternatively, it is possible to use three or more reference parameters (for the other non-reference parameters). 
     In this case as well, the corrections for the (multiple) reference parameters may be combined with other formulas (for example, based on their weighed average, squared mean value, and so on). 
     Similar considerations apply if the correction for each non-reference parameter is obtained in a different way from the intermediate value resulting from the correction of the reference parameter(s)—for example, by rounding it. 
     An embodiment of the present invention lends itself to be put into practice even by choosing any other characteristics of the clock signals (such as their skewness), or more generally any other reference parameters (such as delays, resistances, capacitances, and so on). 
     Although an embodiment of the invention may be particularly advantageous for non-reference parameters that cannot be measured outside the IC, nothing prevents application of this or other embodiments to any functional parameter (even when it may be measured). 
     An IC such as the IC  105  may be coupled to a controller, and the IC and controller may form part of a system such as a cell phone or computing system.