Abstract:
An electronic device including a set of functional block, and a biasing block for generating a set of bias voltages for the functional blocks. The electronic device further includes a holding block coupled between the biasing block and the functional blocks for providing each bias voltage to at least one corresponding functional block, for each bias voltage the holding block including a capacitive element for storing the bias voltage, and a switch element switchable between an accumulation condition wherein provides the bias voltage from the biasing block to the capacitive element and to the at least one corresponding functional block, and a release condition wherein isolates the capacitive element from the biasing block and provides the bias voltage from the capacitive element to the at least one corresponding functional block, and a control block for alternately switching the switching elements between the accumulation condition and the release condition.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority benefit of Italian patent application number MI2010A001192, filed on Jun. 30, 2010, entitled BACKGROUND POWER CONSUMPTION REDUCTION OF ELECTRONIC DEVICE, which is hereby incorporated by reference to the maximum extent allowable by law. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The solution according to one or more embodiments of the present invention relates to the field of electronic devices. More specifically, the solution relates to the reduction of a power consumption of electronic devices. 
         [0004]    2. Discussion of the Related Art 
         [0005]    Since some time the market of electronic products is increasingly focusing on products with low power consumption, particularly in the case of mobile products (e.g., computers, mobile phones and personal digital assistants). These mobile products include electronic devices (central processing unit, memory, display, etc.) for performing different operations. In particular, the electronic devices included in a generic mobile product should meet two main specifications. A first specification relates to a physical area occupation, which should be as small as possible in order to ensure the implementation of more electronic devices in the same mobile product or to reduce the size thereof. A second specification relates to a power consumption needed to operate such mobile devices. In more detail, such power is supplied by batteries which have a limited availability of energy. It is therefore desirable to reduce the power consumption of all the electronic devices included in the mobile products in order to increase the autonomy of such portable products with the same batteries used. 
         [0006]    In particular, it is possible to identify two distinct phases of power consumption in an electronic device. A first phase is a phase of active power consumption associated with an operating condition of the electronic device (i.e., a period in which it actively performs an operation for which it was designed). A second phase is a phase of static power consumption associated with a standby condition of the electronic device; in this standby condition, the electronic device performs no operation but it is simply kept on to be ready to switch from the standby condition to the operating condition. 
         [0007]    In general the standby condition of the electronic device may have a very long duration (e.g., several hours) during which the static power consumption unnecessarily dissipates energy stored in the batteries, thus reducing the autonomy of the corresponding portable device. 
         [0008]    In the prior art various expedients have been implemented to reduce power consumption. Substantially these expedients are based on two different approaches. A first approach consists of partially or completely disabling the electronic devices in the standby condition; this dramatically reduces the static power consumption, but at the same time also the performance of the electronic device, as it requires a relatively long time to switch from the standby condition to the operating condition (needed for its bias voltages to reach a desired value thereof in a stable way). 
         [0009]    A second approach involves the implementation of complex systems to manage the supplying of bias voltages in an advantageous way; in this case there is a substantial increase in the required area needed to implement the electronic devices, not always available in portable products; in addition, this enables a smaller reduction of the power consumption than the previous approach does, since such systems in turn consume some power for their correct operation. 
         [0010]    This problem is particularly acute in programmable memory devices of the electrically/erasable type or EEPROM (“Electrically Erasable Programmable Read-Only Memory”). In fact, such memory devices use bias voltages of very high value (generally higher than a supply voltage of the corresponding portable products), which implies non-negligible power consumption. 
       SUMMARY OF THE INVENTION 
       [0011]    In general terms, a solution according to one or more embodiments is based on the idea of storing the bias voltages in capacitive elements. 
         [0012]    In particular, one or more aspects of a solution according to specific embodiments are set out in the independent claims, with advantageous features of the same solution that are set out in the dependent claims (whose wording is herein incorporated verbatim by reference). 
         [0013]    More specifically, an aspect of a solution according to an embodiment provides an electronic device. The electronic device includes a set of functional blocks (e.g., a read/write unit and memory cells), and a biasing block for generating a set of bias voltages for the functional blocks. In the solution according to an embodiment, the electronic device further includes a holding block coupled between the biasing block and the functional blocks for providing each bias voltage to at least one corresponding functional block. For each bias voltage, the holding block includes a capacitive element (for storing the bias voltage), and a switching element; the switching element is switchable between an accumulation condition (wherein it provides the bias voltage from the biasing block to the capacitive element and to the corresponding at least one functional block), and a release condition (wherein it isolates the capacitive element from the biasing block and provides the bias voltage from the capacitive element to the corresponding at least one functional block). The electronic device further includes a control block for alternately switching the switch elements between the accumulation condition and the release condition. 
         [0014]    Another aspect of a solution according to an embodiment provides a corresponding method (with the same advantageous features recited in the dependent claims for the memory device which apply mutatis mutandis to the method). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    A solution according to one or more embodiments, as well as additional features and its advantages will be better understood with reference to the following detailed description, given purely by way of a non-restrictive indication and without limitation, to be read in conjunction with the attached figures (wherein corresponding elements are denoted with equal or similar references and their explanation is not repeated for the sake of brevity). In this respect, it is expressly understood that the figures are not necessarily drawn to scale (with some details that may be exaggerated and/or simplified) and that, unless otherwise specified, they are simply intended to conceptually illustrate the structures and procedures described herein. In particular: 
           [0016]      FIG. 1  shows a principle block diagram of an EEPROM memory device wherein an embodiment is applicable; 
           [0017]      FIG. 2  shows a principle circuit diagram of a holding block of the memory device according to an embodiment; 
           [0018]      FIG. 3  shows a principle block diagram of a biasing block and of a control block of the memory device according to an embodiment; 
           [0019]      FIG. 4  shows a principle circuit diagram of a generator block included in the control block according to an embodiment, and 
           [0020]      FIG. 5  shows a principle block diagram of a state machine included in the control block according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    With particular reference to  FIG. 1 , there is shown a principle block diagram of a memory device  100 , in which an embodiment is applicable; more specifically, the memory device  100  is an EEPROM-type memory device. The memory device  100  includes a matrix of memory cells  105  (not shown individually in the figure), which is organized into rows and columns. The memory device  100  also includes a row decoder  115   r  and a column decoder  115   c.  The access to the memory cells  105  of a selected word (in reading and writing) is made by decoding a row address ADRr and a column address ADRc, which are supplied to the row decoder  115   r  and to the column decoder  115   c,  respectively. The column decoder  115   c  selectively connects the memory cells  105  to a read/write unit  120 , which contains circuitry used to read and write the selected memory cells  105  (e.g., driving circuits and comparators). A biasing block  125  provides a plurality of bias voltages Vbias needed for the operation of various blocks of the memory device  100  (and in particular, to be applied to the read/write unit  120  and to be applied to memory cells  105  through the row decoder  115   r ). A micro-controller  128  manages the operation of the entire memory device  100  (in particular, by interfacing with the read/write unit  120 ). 
         [0022]    According to an embodiment, (as described in detail hereinbelow), the biasing block  125  provides the bias voltages Vbias to a holding block  130 , through a plurality of bias lines Lin. The holding block  130  in turn transfers bias voltages Vbias′ corresponding to the bias voltages Vbias, through bias lines Lout, to the read/write unit  120  and to the decoder  115   r . Moreover, the biasing block  125  provides a reference bias voltage (for example, of bandgap) Vbg (included among the bias voltages Vbias) to a control block  135 . The control block  135  also receives an enable signal EN and a register signal Reg from the micro-controller  128 . The control block  135  sends a control signal SH to the holding block  135 , to the biasing block  125  and to itself. 
         [0023]      FIG. 2  shows a principle circuit diagram of the holding block  130  according to an embodiment. For each bias line Lin i  (where the subscript i denotes a value between 1 and a number N equal the total number of bias lines Lin) and a corresponding bias line Lout i  (belonging to the bias lines Lout), the holding block  130  includes a controlled switch S i  and a holding capacitor C i . In more detail, the switch S i  has a control terminal receiving the control signal SH (coming from the control block, not shown), a first conduction terminal connected to the bias line Lin i , and a second conduction terminal connected to the bias line Lout i . Such switch S i  may include, for example, a PMOS-type transistor and a shifter circuit adapted to receive the control signal SH and convert it to a control voltage adapted to open and close the switch S i  according to a logic value of the control signal SH. Moreover, the bias line Lin i  is connected to a first terminal of the capacitor C i , while a second terminal thereof is connected to a ground terminal of the memory device for receiving a reference (or ground) voltage. 
         [0024]    The operation of the holding block  130  is the following. The biasing block (not shown in the figure) provides a corresponding bias voltage Vbias i  (included among the bias voltages Vbias) to the bias line Lin i . 
         [0025]    When the control signal SH is asserted (e.g., at a high logic value equal to a supply voltage of the memory device) the switch S i  is closed thereby coupling the bias line Lin i  with the bias line Lout i ; in this way, the bias line Lout provides a corresponding bias voltage Vbias i ′=Vbias i  (included among the bias voltages Vbias′) to the corresponding blocks of the memory device (e.g., the read/write unit and the memory cells, not shown in the figure). At the same time, the capacitor C i  is charged to the same bias voltage Vbias i ′=Vbias i . When the control signal SH is de-asserted (e.g., at a low logic value equal to the ground voltage) the switch S i  is opened thereby decoupling the bias line Lin i  from the bias line Lout i . However, the bias line Lout i  is maintained at the bias voltage Vbias i ′=Vbias i  by the capacitor C i . In such condition, the blocks connected to the bias line Lout i  still work correctly since they receive the same bias voltage Vbias i ′ necessary for their operation (even if the biasing block is turned off, as will be described in detail below). In such condition, due to inevitable leakage currents, the capacitor C i  will discharge slightly from the bias voltage Vbias i  toward the ground voltage, thereby reducing the bias voltage Vbias i ′ correspondingly. 
         [0026]    The control signal SH is then asserted again, so as to recharge the capacitor C i  to the bias voltage Vbias i  (at the same time turning on again the biasing block that provides the bias voltage Vbias i )—with the same operations above described that are cyclically repeated. 
         [0027]    Consequently, the bias voltage Vbias i ′ (provided to the blocks connected to the bias line Lout i ) will have a value that oscillates slightly over time under the bias voltage Vbias i . However, this ripple has a predetermined maximum width so as not to cause any problem to the proper operation of the memory device. 
         [0028]    In this way, it is possible to achieve a high reduction in power consumption associated with the memory device as a whole. In fact, according to an embodiment there is power consumption (i.e., energy is absorbed by an energy source outside the memory device—e.g., a battery) only during the times when the control signal SH is asserted. Therefore, the power consumption is reduced proportionally to the time when the control signal SH is maintained de-asserted. 
         [0029]    In contrast, an alternative embodiment differs from what has been previously described as follows. In an operating condition of the memory device, the control signal SH is always asserted. In this way, the holding block  130  does not interfere with the operation of the memory device (once the capacitor C i  is charged at the bias voltage Vbias i  applied to the bias line Lin i , which is directly transferred to the bias line Lout i ). In a standby condition, instead, the control signal SH is cyclically asserted and de-asserted as described above. This alternative embodiment thus allows reducing the power consumption in the standby condition only; it is particularly advantageous in the case wherein the functional blocks (not shown in the figure) require a high power consumption and/or a high precision of the biasing voltage in the operating condition (not sustainable by the capacitors C i ). 
         [0030]    In an embodiment, the capacitors C i  are implemented using stabilization capacitors already present on the connecting lines Lout i . These stabilization capacitors are normally used to reduce fluctuations of the voltage/current on the bias lines Lout i . In this way, there is no need to add more capacitors to the bias lines Lout i ; this allows saving area of the memory device and not increasing the total capacity on the bias lines Lout i . Consequently, no delays in the operation of the memory device are introduced (i.e., the performance thereof is not affected). 
         [0031]    The capacitors C i  do not have necessarily the same capacity; in fact, they may be advantageously sized according to the value of the corresponding bias voltages Vbias i  and according to a maximum value of an operating current (in the operating condition of the memory device) and/or of a leakage current (in the standby condition of the memory device) drawn by the blocks connected to the corresponding bias lines Lout i . For example, the values of the capacities of the capacitors C i  may vary from a few pF to a few tens of pF. 
         [0032]    Referring now to  FIG. 3 , it illustrates a principle block diagram of the biasing block  125  and of the control block  135  according to an embodiment of the invention. 
         [0033]    The biasing block  125  has a power supply terminal VDD pol , which receives a supply voltage VDD of the memory device (e.g., 1.8-3V). The biasing block  125  includes a functional circuit  305  (e.g., formed by charge pumps and bandgap generators), which generates all the bias voltages Vbias from the supply voltage VDD (e.g., from 1 to 10V). 
         [0034]    According to an embodiment, the biasing block  125  includes a controlled switch S pol  having a first conduction terminal connected to the power supply terminal VDD pol , a second conduction terminal connected to an input terminal of the functional circuit  305 , and a control terminal for receiving the control signal SH. Some holding capacitors (all denoted with the same reference C pol ) are connected to corresponding nodes of the biasing block  125 , which are essential for the fast restart thereof (during the charging of the capacitors of the holding block). For example, a capacitor C pol  is connected to each of the bias lines Lin (only one shown in the figure), and other capacitors C pol  are arranged within the functional circuit  305  (only one shown in the figure). 
         [0035]    The operation of the biasing block  125  is the following. 
         [0036]    When the control signal SH is asserted (high logic value) the switch S pol  is closed thereby connecting the input terminal of the functional circuit  305  to the power supply terminal VDD pol . At the same time, each capacitor C pol  is loaded to the corresponding voltage. 
         [0037]    When the control signal SH is de-asserted (low logic value) the switch S pol  is open thereby decoupling the input terminal of the functional circuit  305  from the power supply terminal VDD pol . However, each bias line Lin is held at the corresponding bias voltage by its capacitor C pol . In this condition, the functional circuit  305  absorbs energy from the capacitors C pol , which then discharge slightly, thereby correspondingly reducing the supplied voltages. 
         [0038]    The control signal SH is then asserted again, in order to recharge the capacitors C pol  to the corresponding voltage—with the same operations described above that are cyclically repeated. 
         [0039]    In this way, it is possible to further reduce the power consumption of the memory device (since as hereinabove there is a power consumption only during the times wherein the control signal SH is asserted, so that the power consumption is scaled down with the time wherein the control signal SH is maintained de-asserted). 
         [0040]    The control block  135  instead includes a generator block  310 , which generates a further reference voltage VIref from the reference voltage Vbg received from the biasing block  125 . An oscillator block  315  (implemented in a way known in the art and therefore not described in detail) receives the reference voltage VIref and generates a periodic clock signal Clk with a period T proportional to the value thereof. A state machine  320  receives the clock signal Clk from the oscillator block  315 , and also receives the enable signal EN and the register signal Reg from the micro-controller (not shown in the figure). In particular, the enable signal EN may be either a signal dedicated to enable the control block  135  or a general enable signal commonly used to enable the memory device as a whole. According to the enable signal EN, the register signal Reg and the clock signal Clk, the state machine  320  generates the control signal SH which is supplied to the biasing block  125  and to the holding block  130 , and it is also supplied to the generator block  310 . In particular, following a first assertion of the enable signal EN (corresponding to a start up of the memory device) an initialization phase is started in which the control signal SH is asserted for a predetermined number J of periods of the clock signal Clk to allow the charging of all the holding capacitors of the memory device to the respective voltages. After the initialization phase, the control signal SH is de-asserted for a number N of periods T of the clock signal Clk determined by the register signal Reg (to turn off the biasing block and to open the switches). At the end of the number N of periods T, the control signal SH is asserted for a predetermined number M of periods T of the clock signal Clk (to turn on the biasing block and close the switches). The same operations described above are cyclically repeated (until the enable signal EN is not de-asserted). 
         [0041]    The above-described structure allows programming, by means of the register signal Reg, the duration of a release condition (control signal SH de-asserted) of the holding capacitors (in which they discharge). Such register signal Reg allows varying the duration of the release condition from a minimum value to a maximum value (e.g., from 5 μs to 130 μs with an increment step of 5-20 μs) according to a maximum acceptable ripple of the voltages at the holding capacitors that does not compromise the performance of the memory device. A subsequent accumulation condition (control signal SH asserted) of the holding capacitors (in which they are recharged) has instead a fixed duration, which is chosen so as to ensure a full recharge of the holding capacitors for any duration of the discharge period. 
         [0042]      FIG. 4  illustrates a principle circuit diagram of the generator block  310  according to an embodiment. The generator block  310  includes an operational amplifier  405  having a non-inverting input terminal (+) for receiving the reference voltage Vbg (from the biasing block, not shown in the figure), and an inverting input terminal (−) connected to a ground terminal (for receiving the ground voltage) through a resistor  407 . An output terminal of the operational amplifier  405  is connected to an intermediate node Ni. A PMOS output transistor  415  has a drain terminal connected to the inverting terminal of the operational amplifier  405 , and a gate terminal connected to the node Ni. A controlled switch Sin 1  has a first conduction terminal connected to a power supply terminal VDD gen  (for receiving the supply voltage VDD), a second conduction terminal connected to a supply terminal of the operational amplifier  405 , and a control terminal for receiving the control signal SH. Another controlled switch Sin 2  has a first conduction terminal connected to the power supply terminal VDD gen , a second conduction terminal connected to a source terminal of the transistor  415 , and a control terminal for receiving the control signal SH. The generator block  310  also includes a holding capacitor Cin connected between the node Ni and the power supply terminal VDD gen . 
         [0043]    A PMOS transfer transistor  425  has a gate terminal connected to the node Ni, a source terminal connected to the power supply terminal VDD gen , and a drain terminal connected to a first conduction terminal of a controlled switch Sout 1 . The switch Sout 1  has a control terminal for receiving the control signal SH and a second conduction terminal connected to a gate terminal of a NMOS transdiode transistor  440 , which is connected to an output node Nout that provides the reference voltage Viref; the transistor  440  has a source terminal connected to the ground terminal. A further controlled switch Sout 2  has a first conduction terminal connected to the node Nout, a second conduction terminal connected to a drain terminal of the transistor  440 , and a control terminal for receiving the control signal SH. A further holding capacitor Cout is connected between the node Nout and the ground terminal. 
         [0044]    The operation of the generator block  310  is the following. 
         [0045]    When the control signal SH is asserted (high logic value) all the switches Sin 1 , Sin 2 , Sout 1  and Sout 2  are closed thereby connecting the power terminal of the operational amplifier  405  and the source terminal of the transistor  415  with the power supply terminal VDDgen, and the drain terminal of the transistor  425  and the drain terminal of the transistor  440  with the gate terminal of the transistor  440 . As a result of a negative feedback, the operational amplifier  405  reproduces the reference voltage Vbg across the resistor  407  that conducts a reference current Ibg equal to the ratio between the reference voltage Vbg and a resistance of the resistor  407 . Such current Ibg flows completely through the transistor  415  (since the inverting input terminal of the operational amplifier  405  has infinite resistance), so that a corresponding intermediate voltage Vi is set to the gate terminal of the transistor  415 ; the voltage Vi is also set to the node Ni, thereby charging the capacitor Cin to the same. The voltage Vi is also applied to the gate terminal of the transistor  425 , which determines a corresponding current Idout through the transistor  425 , which depends on the relationship between the form factors (e.g., the ratio between width and length in MOS field effect transistors) of the transistors  425  and  415  (for example, with the currents through the transistors  415  and  425  that are equal if they have the same size). The current Idout charges the capacitor Cout until reaching the reference voltage VIref for which the transistor  440  turns on (diverting the current Idout toward the ground terminal). The generator block  310  then allows generating the reference voltage VIref from the reference voltage Vbg, keeping the non-inverting terminal of the operational amplifier  405  (which receives the reference voltage Vbg) decoupled from the node Vout (which generates the reference voltage VIref), thereby isolating the upstream biasing block from the downstream oscillator block (not shown in the figure). 
         [0046]    When the control signal SH is de-asserted (low logic value) the switches Sin 1 , Sin 2 , Sout 1  and Sout 2  are open. Consequently, the operational amplifier  405  and the transistor  415  are turned off (as they do not receive the supply voltage VDD gen  any longer). However, the node Ni is maintained at the voltage Vin by the capacitor Cin (apart from a slight discharge thereof). At the same time, the node Nout is maintained at the reference voltage Vlref by the capacitor Cout; in this condition, the oscillator (not shown in the figure) receives the reference voltage VIref through the capacitor Cout, which then slightly discharges. 
         [0047]    The control signal SH is then asserted again, so as to recharge the capacitor Cin to the voltage Vin and the capacitor Cout to the reference voltage Viref—with the same operations described above that are cyclically repeated. 
         [0048]    In this way, it is possible to further reduce the power consumption of the memory device (since there is a power consumption only during the times when the control signal SH is asserted, so that the power consumption is reduced with the time wherein the control signal SH is maintained de-asserted). 
         [0049]    The  FIG. 5  illustrates a principle block diagram of the state machine  320  included in the control block (not shown in the figure) according to an embodiment of the invention. The state machine  320  includes a counter  505  and a phase block  510 . Both the counter  505  and the phase block  510  receive the clock signal Clk (from the oscillator, not shown in the figure) and the enable signal EN (from the micro-controller, not shown in the figure). The counter  505  further receives the register signal Reg (from the micro-controller as well), and an accumulation end signal ER from the phase block  510  to which in turn it provides an end of count signal EoC. The phase block  510  generates the control signal SH. 
         [0050]    The operation of the state machine  320  is the following. 
         [0051]    At the end of theinitialization phase of the memory device described above, the phase block  510  impulsively asserts the accumulation end signal ER. In response thereto, the counter  505  is initialized to zero (with the signal EoC that remains de-asserted), and it is incremented at each period of the clock signal Clk; at the same time, the phase block  510  de-asserts the control signal SH—thereby determining the release condition. When the counter  505  reaches the value N determined by the register signal Reg, it asserts the signal EoC. In response thereto, the phase block  510  asserts the control signal SH—thereby determining the accumulation condition—for a predetermined number M of periods of the clock signal Clk. At the end of the M-th period T of the clock signal Clk the phase block  510  de-asserts the control signal SH again (to return to the release condition); at the same time, the phase block  510  impulsively asserts the signal ER, which re-initializes the counter  505  to cyclically repeat the same operations described above (until the enable signal EN is de-asserted). 
         [0052]    Naturally, in order to satisfy local and specific requirements, a person skilled in the art may apply to the solution described above many logical and/or physical modifications and alterations. More specifically, although this solution has been described with a certain degree of particularity with reference to one or more embodiments thereof, it should be understood that various omissions, substitutions and changes in the form and details as well as other embodiments are possible. Particularly, different embodiments of the invention may even be practiced without the specific details (such as the numerical examples) set forth in the preceding description to provide a more thorough understanding thereof; conversely, well-known features may have been omitted or simplified in order not to obscure the description with unnecessary particulars. Moreover, it is expressly intended that specific elements and/or method steps described in connection with any embodiment of the disclosed solution may be incorporated in any other embodiment as a matter of general design choice. 
         [0053]    For example, similar considerations apply if the memory device has a different architecture or includes equivalent components (either separated or combined, in whole or in part). In addition, the memory device may have different operating characteristics; for example, the signals may be asserted and de-asserted at different reference voltages (even reversed to each other). 
         [0054]    Nothing prevents from arranging the holding block to provide bias voltages to other functional blocks of the memory device, such as system oscillators and/or control and driving circuits of the charge pumps. 
         [0055]    Furthermore, the holding block may be distributed instead of concentrated, i.e., a controlled switch and a holding capacitor may be provided directly to a terminal for receiving the respective bias voltage of each functional block of the memory device. 
         [0056]    Obviously, the controlled switches may be implemented differently—for example, by using transistors with different doping, bipolar transistors or pass-gates. 
         [0057]    Alternatively, the control block may alternately switch the switches between the accumulation condition and the release condition in any other condition of the memory device (for example, only in a energy-saving operating condition). 
         [0058]    Nothing prevents from implementing dedicated holding capacitors to be used with or instead of the stabilization capacitors already provided in the memory device. 
         [0059]    In addition, the control block may have an equivalent structure (e.g., without requiring a dedicated oscillator). Alternatively, more control signals may be generated to control different functional blocks in a specific way. 
         [0060]    Nothing prevents from maintaining the biasing block always supplied or to provide more than one switch in the functional block—for example, a switch for each charge pump and bandgap circuit included in the functional circuit. 
         [0061]    Moreover, the generator block may be provided with a greater/lower number of holding capacitors and switches. 
         [0062]    Similarly, also the generator block may have a structure different from the described one. 
         [0063]    Alternatively or in addition, both the accumulation and release conditions may be made programmable or both constant and predetermined. 
         [0064]    Nothing prevents from implementing the solution in a device different from an EEPROM-type memory; for example, an embodiment may be implemented in acquisition devices (such as analog-to-digital converters and samplers). 
         [0065]    The proposed solution lends itself to be implemented by an equivalent method (using similar steps, removing some steps being not essential, or adding further optional steps); moreover, the steps may be performed in different order, in parallel or overlapped (at least in part). 
         [0066]    It should be readily apparent that the proposed solution might be part of the design of an integrated device. The design may also be created in a programming language; in addition, if the designer does not manufacture the integrated device or its masks, the design may be transmitted through physical means to others. Anyway, the resulting integrated device may be distributed by its manufacturer in the form of a raw wafer, as a naked chip, or in packages. 
         [0067]    Moreover, the memory device may be integrated with other circuits in the same chip, or it may be mounted in intermediate products (such as motherboards) and coupled with one or more other chips (such as a processor). In any case, the memory device is adapted to be used in complex systems (such as a mobile phone). 
         [0068]    Having thus described at least one illustrative embodiment of the invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and the scope of the present invention. Accordingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited only as defined in the following claims and the equivalents thereto.