Battery charge level monitoring circuit and method

Abstract

Battery Charge Level Monitoring Circuit and Method This description relates to a device comprising a rechargeable battery (102); a first circuit (11) comprising a processor (118) and a voltage comparator (112) configured to compare the rechargeable battery voltage (VBAT) to a limit voltage; and a second circuit (13), connected to the first circuit (11), comprising a non-volatile memory (132) and configured to initialize the processor (118) of the first circuit if the rechargeable battery voltage (VBAT) is greater than the limit voltage. Figure for the abstract: Fig. 3

Description

Title of the invention: Circuit and method for monitoring the charge level of a battery. Technical field

[0001] This description relates generally to electronic devices comprising a rechargeable battery and more particularly to a circuit and a method for monitoring the charge level of a battery. Previous technique

[0002] An electronic device can be powered by a rechargeable battery. However, if the battery charge level becomes too low, some of the device's circuits may no longer function correctly, and it may be preferable to reset the device. To avoid such a situation, the battery charge level can be assessed before starting all or part of the device, and during device operation.

[0003] Monitoring the charge level of a battery generally involves measuring the voltage across the terminals of the rechargeable battery using an analog-to-digital converter (ADC) and comparing the measured voltage with a threshold. However, existing solutions are not suitable for all applications, particularly when a relatively low cost and chip area are desirable. Summary of the invention

[0004] Embodiments of the present application are capable of overcoming all or part of the problems existing in the prior art.

[0005] According to a first aspect, a device comprising: - a rechargeable battery; - a first circuit comprising a processor and a voltage comparator configured to compare the voltage of the rechargeable battery to a limiting voltage; and - a second circuit, connected to the first circuit, comprising a non-volatile type memory and configured to initialize the processor of the first circuit if the voltage of the rechargeable battery is greater than the limit voltage.

[0006] According to one embodiment, the memory of the second circuit is a flash type memory.

[0007] According to one embodiment, the device further includes a voltage regulator configured to supply the first and second circuits with voltage.

[0008] According to one embodiment, the first circuit comprises a connection terminal linked to a connection terminal of the second circuit, a signal present at the terminal of connection of the first circuit being either in a first state or in a second state, depending on the charge level of the rechargeable battery.

[0009] According to one embodiment, the signal present at the connection terminal of the first circuit is in the second state if the battery voltage is less than the limit voltage.

[0010] According to one embodiment, the second circuit is configured to reset the processor and / or generate an alert signal if the signal present at the connection terminal of the first circuit is in the second state.

[0011] According to one embodiment, the voltage of the connection terminal of the first circuit in the first state is greater than the voltage of the connection terminal of the first circuit in the second state.

[0012] According to one embodiment, the first circuit further includes an analog-to-digital converter configured to generate a digital value representative of the voltage of the rechargeable battery.

[0013] According to one embodiment, the rechargeable battery is a lithium battery.

[0014] According to another aspect, a process is envisaged comprising: - the comparison, by a first circuit, of the voltage of a rechargeable battery with a limiting voltage; and - the initialization of a processor of the first circuit, by a second circuit including a non-volatile type memory, if the voltage of the rechargeable battery is greater than the limit voltage.

[0015] According to one embodiment, the method also includes, before the execution of a program by the processor, comparing the voltage of the rechargeable battery to a threshold voltage, and executing the program only if the voltage of the rechargeable battery is greater than the threshold voltage.

[0016] According to one embodiment, the method also includes resetting the processor and / or emitting an alert signal by the second circuit if the voltage of the rechargeable battery is below the limit voltage. Brief description of the drawings

[0017] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0018] Fig. 1 represents schematically and in block form a device comprising a rechargeable battery according to one embodiment;

[0019] [Fig.2] is a flowchart representing operations of a method for monitoring the voltage of a rechargeable battery, at the start-up of the device of [Fig.1], according to an embodiment of the present application;

[0020] [Fig.3] represents schematically and in block form the device of [Fig.1] in more detail;

[0021] [Fig.4] is a flowchart representing operations of a method for monitoring the voltage of a rechargeable battery according to another embodiment of the present application;

[0022] [Fig. 5] is a graph representing an example of the evolution of certain voltages of the device in [Fig. 3], according to one embodiment; and

[0023] [Fig.6] is a graph representing another example of the evolution of certain tensions of the device of [Fig.3], according to one embodiment. Description of the implementation methods

[0024] The same elements have been designated by the same reference numerals in the different figures. In particular, structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0025] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0026] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0027] Unless otherwise specified, the expressions "approximately", "roughly", and "in the order of" mean within 10%, preferably within 5%.

[0028] Fig. 1 represents schematically and in block form a device 100 comprising a rechargeable battery 102 according to one embodiment.

[0029] The device 100 comprises a first circuit 11 (“COPROCESSOR”) and a second circuit 13 (“EXTERNAL HOST”). In one example, the circuit 13 is a host of the device 100 comprising a first processor (not shown in [Fig. 1]), and the circuit 11 is a coprocessor comprising a processor 118 (“PROCESSOR”). The circuit 11 is, for example, implemented by a first integrated circuit, and the circuit 13 is, for example, implemented by a second integrated circuit external to the first integrated circuit.

[0030] The rechargeable battery 102, for example a lithium battery, has a voltage VBAT between its terminals which varies according to its charge level. The battery 102 is connected to a ground rail 104 of the device 100 and supplies voltage to the circuit 11 via the via a connection terminal 110 of the first circuit 11. The battery 102 supplies voltage to circuit 13 via a voltage regulator 106 ("REG"). The voltage regulator 106 applies, for example, a gain to the voltage VBAT so that the output voltage of the voltage regulator 106 is within a voltage range compatible with the digital circuits of circuit 13. The voltage VBAT is, for example, between 0V and 6V and, for example, between 0V and 4.5V depending on the battery's charge level. The output voltage of the voltage regulator is, for example, between 0V and 4V and, for example, between 0V and 2V, depending on the setpoint voltage of the voltage regulator 106 and / or the charge level of battery 102. The output voltage of the regulator is connected to a connection terminal 130 of circuit 13.

[0031] Circuit 13 is powered by a supply voltage lower than that which powers circuit 11. Thus, if the rechargeable battery 102 is no longer sufficiently charged and the voltage VBAT becomes lower than the supply voltage of circuit 11, circuit 13 remains operational and emits, for example, an alert signal to notify a user that a battery recharge is required.

[0032] The circuit 11 includes, for example, a connection terminal 119 connected to the rail of mass 104 of device 100.

[0033] The circuit 11 includes a comparator 112 (“COMPARATOR”) to which the The voltage VBAT of terminal 110 and the processor 118. The comparator 112 is configured to compare the voltage VBAT to a limit voltage VLIM (not shown in [Fig. 1]). The limit voltage VLIM corresponds, for example, to the minimum operating voltage of at least one circuit of the device 100, for example, the processor 118. The VLIM voltage is, for example, between 1 and 3 V and, for example, between 2.6 and 2.8 V.

[0034] According to one embodiment, the output voltage of comparator 112 is in a first state, for example a high voltage state, if VBAT is greater than VLIM and in a second state, for example a low voltage state, if VBAT is less than VLIM.

[0035] According to another embodiment, the voltage VBAT is compared to the limit voltage VLIM and to a second limit voltage, the second limit voltage being greater than the voltage VLIM. For example, the limit voltage VLIM is equal to 2.7V and the second limit voltage is equal to 2.73V. The output voltage of comparator 112 is in the first state if VBAT is greater than the second limit voltage, and the output voltage of comparator 112 is in the second state if VBAT is less than the voltage VLIM. The output voltage of comparator 112 remains unchanged if VBAT is between the two limit voltages. This embodiment incorporates hysteresis to prevent oscillation of the comparator 112 output signal when VBAT is close to the comparator's trip point.

[0036] The output voltage of comparator 112 is connected to a connection terminal 114 of circuit 11.

[0037] The voltage at terminal 114, marked "NRST", is indicative of the state of charge of battery 102.

[0038] When the voltage VBAT becomes less than the limit voltage VLIM, the voltage NRST enters the second state and the circuit 11 transitions, for example, into a reset state.

[0039] In some embodiments, the first circuit 11 is configured to maintain the second state even if the battery voltage VBAT falls below a minimum level for the proper operation of the circuit 11. Furthermore, the first circuit 11 is, for example, configured to maintain the first state as long as the battery voltage VBAT remains above the minimum level for the proper operation of the circuit 11, and otherwise, to switch to the second state. Indeed, the choice of a low voltage state for the second state and of powering the comparator 112 with the VBAT voltage ensures that, if the VBAT voltage falls below the limit voltage threshold VLIM, then the NRST voltage will naturally decrease towards the low voltage state, indicating a low level in the battery 102.

[0040] The second circuit 13 includes a non-volatile memory 132 (MEM), used at the start-up of the device 100.

[0041] Circuit 13 includes a connection terminal 134 connected to the connection terminal 114 of circuit 11. Circuit 13 is configured, for example, to evaluate the charge level of battery 102 by reading the NRST voltage at terminal 134. According to one embodiment, if NRST is in the second state, then the battery is not sufficiently charged and circuit 13 emits an alert signal, for example to the user of device 100, for example via a connection terminal 136 (“OUT”), and a signaling device such as an LED or a sound signal generator.

[0042] The second circuit 13 includes for example a connection terminal 138 connected to the ground rail 104 of the device 100 and includes for example a connection terminal 139 connected to a connection terminal 116 of the first circuit 11.

[0043] The connection terminal 116 is connected to the processor 118 of circuit 11 so that circuit 13 can communicate with the processor 118. Communication is carried out, for example, according to SPI (Serial Peripheral Interface) or SDIO (Secure Digital Input Output) protocols, for example via a data bus. For example, an SPI interface between the connection terminal 139 and the connection terminal 116 is equipped with a MOSI (Master Output, Slave Input) data line to transmit data from circuit 13 to circuit 11 and a MISO (Master Input, Slave Output) data line to transmit data from circuit 11 to circuit 13. In another example, an SDIO interface between connection terminal 139 and connection terminal 116 is also equipped with one communication line in each direction or several, for example 4, communication lines in each direction, multiplying the communication speed between circuits by that amount.

[0044] According to one embodiment, the circuit 11 does not include non-volatile memory and includes, for example, volatile memory, for example, random access memory (RAM). The initialization of the processor 118 is performed by the circuit 13, for example, by loading binary code into the RAM. For example, binary code stored in the memory 132 of the circuit 13 is loaded into the RAM when the processor 118 starts up. The processor 118 is, for example, configured to read and execute the binary code.

[0045] According to one embodiment, the processor 118 is connected to the output of the comparator 112 to receive the result of the comparison between the voltage of the battery 102 VBAT and the voltage VLIM.

[0046] Figure 2 is a flowchart representing the operations of a method for monitoring the voltage of a rechargeable battery, for example battery 102 of Figure 1, at the start-up of device 100 of Figure 1, according to an embodiment of the present application. This method is carried out, for example, by comparator 112 and processor 118 of circuit 11 and by circuit 13.

[0047] In a step 200 of the process (“EXT HOST SWITCHED ON”), the circuit 13 is, for example, started. For example, the start-up is triggered manually by the user or automatically, for example by a low-power timer integrated into the circuit 13. When the circuit 13 starts, at least one binary code is executed by this circuit. The binary code is, for example, stored in the non-volatile memory 132 of the [Fig. 1],

[0048] In a step 202 (“NRST=1?”) following the start-up of circuit 13, circuit 13 is configured, for example, to check the logic state of terminal 134 of [Fig. 1]. If terminal 132 is in the second state (output “NO” of block 202), this means that the voltage VBAT is less than VLIM and that the battery is no longer sufficiently charged for minimal operation of device 100. A signal is, for example, transmitted to the user (block 204, “OUT=1”), for example, an LED is lit, to indicate that the battery needs recharging, and the processor 118 remains off.

[0049] If terminal 134 is in the first state (output "YES" of block 202), this means that the voltage VBAT is greater than VLIM and that the battery is sufficiently recharged to start the processor 118.

[0050] In a step 206 (“EXT HOST UPLOADS CODE IN PROCESSOR”), the circuit 13 loads, for example, a binary code stored in the non-volatile memory 132 to the volatile memory 140 of circuit 11 in [Fig. 1]. The code is transmitted, for example, via an interface, such as a data bus, between connection terminals 139 and 116, and for example according to an SDIO or SPI protocol. The transmitted code allows, for example, the initialization of the processor 118 of circuit 11, which does not, for example, include non-volatile memory.

[0051] In a step 207 (“COPROCESSOR EXECUTES CODE”), the processor 118 of the circuit 11 executes the binary code, for example following a code verification step.

[0052] Fig. 3 represents schematically and in block form the device 100 of Fig. 1 in more detail.

[0053] Some elements of [Fig.3] are identical to elements of [Fig.1]. They are represented with the same reference and will not be detailed again.

[0054] According to one embodiment, the rechargeable battery 102 is connected between the ground rail 104 of the device 100 on the one hand and the connection terminal 110 of the circuit 11 as well as to the voltage regulator 106 on the other hand.

[0055] The voltage regulator 106 applies, for example, a gain to the voltage VBAT so that the output voltage of the regulator is within a voltage range compatible with the digital circuits of the device 100. The output voltage of the regulator is connected to a connection terminal 310 (“VDDIO”) of the circuit 11 and to a connection terminal 330 (“VDD”) of the circuit 13.

[0056] According to one embodiment, the circuit 13 is configured to be powered by a supply voltage lower than VLIM, for example between 1.6V and 2V, for example 1.8V ± 10%. The output voltage of the voltage regulator then corresponds to the supply voltage of the circuit 13.

[0057] According to another embodiment, the circuit 13 is configured to be powered by a supply voltage ALIM higher than VLIM, for example between 2.8V and 3.2V. When VBAT is greater than ALIM, the voltage regulator 106 is configured to generate the ALIM voltage. When VBAT is less than ALIM, the voltage regulator 106 is configured to generate a voltage that follows the variation of the VBAT voltage.

[0058] The voltage VBAT at terminal 110 of circuit 11 is, for example, divided by a voltage divider 311, for example, composed of two resistors connected in series between terminal 110 and the ground rail 104, with an intermediate node between the resistors providing the divided voltage. The divided voltage is compared to the limit voltage VLIM by comparator 112 (“VBAT Monitor”). The output voltage of comparator 112 is, for example, in the first state if VBAT is less than VLIM and, for example, in the second state if VBAT is greater than VLIM.

[0059] The output 312 of comparator 112 is connected for example to an input of an OR logic gate 314. The logic gate 314 includes for example other inputs connected to fault detection circuits (not illustrated in [Fig.3]) present in circuit 11 and which are in the first state in case of fault detection.

[0060] The output of logic gate 314 will be in the first state if at least one of its inputs is in the first state, and in the second state if all the inputs of logic gate 314 are in the second state. According to one embodiment, the output of logic gate 314 is in the first state in the event of a fault detected in circuit 11 or when battery 102 is no longer sufficiently charged.

[0061] The output of logic gate 314 is, for example, connected to the gate of a transistor 315, which is, for example, an n-channel MOS transistor (nMOS). The source of transistor 315 is connected to ground rail 104, and the drain of transistor 315 is connected to terminal 114 and to one electrode of a resistor 316. The state of the NRST voltage at terminal 114 is the opposite of the state of the voltage at the gate of transistor 315. The second electrode of resistor 316 is connected to terminal 310. Electrode 316 is a pull-up resistor and reduces conduction between terminal 310 and ground rail 104 when transistor 315 is activated.

[0062] The NRST voltage is indicative of the state of charge of battery 102.

[0063] The arrangement of transistor 315 allows the second state at terminal 114 to be maintained even if the battery voltage VBAT falls below a minimum level required for the proper operation of circuit 11. Furthermore, transistor 315 allows the first state at terminal 114 to be maintained as long as the battery voltage VBAT remains above the minimum level required for the proper operation of circuit 11, and otherwise, to switch to the second state. The choice of a low-voltage state for the second state and of supplying terminal 114 with the VBAT voltage ensures that, if the VBAT voltage falls below the limit voltage threshold VLIM, then the NRST voltage will naturally decrease towards the low-voltage state, indicating a low level in battery 102.If the processor 118 of circuit 11 is off, the other inputs of logic gate 314 are, for example, fixed at the low voltage level, and only the input corresponding to the voltage level 312 of battery 102 can vary. The NRST voltage 114 therefore remains indicative of the battery voltage level VBAT before the processor 118 of circuit 11 is turned on.

[0064] The drain of transistor 315 is for example also connected to the processor 118 (“PROCESSOR”) of the first circuit 11. The processor 118 takes into account for example a fault detected in the device 100 and the charge level of the battery via the level of the NRST voltage present at the drain of transistor 315.

[0065] The processor 118 of circuit 11 is, for example, connected to a module 317 of circuit 11. The module 317 is, for example, connected to a connection terminal 119 of circuit 11, which is, for example, connected to the ground rail 104 of device 100. The module 317 is, for example, connected to terminal 110 to be powered by the voltage VBAT and is, for example, configured to perform functions of device 100, for example, establishing wireless communication with an external device not shown in [Fig. 3]. The module 317 includes, for example, a voltage measurement circuit 318 (“VBAT Measurement ADC”) comprising an analog-to-digital converter.

[0066] According to one embodiment, when VBAT is greater than VLIM, circuit 11 measures the value of the voltage VBAT via the voltage measuring circuit 318 and transmits the value of VBAT to circuit 13 via connection terminals 116 and 139. Circuit 11 is, for example, configured to be able to operate in different operating modes, for example, a mode consuming less energy if the voltage VBAT is less than a fixed voltage, greater than the limit voltage VLIM, for example, 3V. Depending on the value of VBAT, circuit 13 is, for example, configured to control the operating mode of circuit 11.

[0067] In certain embodiments, before a program is executed by the processor 118 of the circuit 11, the voltage VBAT of the rechargeable battery 102 is compared with a threshold voltage VTH to verify that the voltage VBAT is above this threshold. The threshold voltage VTH corresponds, for example, to a minimum voltage for the proper execution of the program. The optional consideration of the threshold voltage VTH will now be described in relation to [Fig. 4].

[0068] The [Fig.4] is a flowchart representing operations of a method for monitoring the voltage of a rechargeable battery by the circuit 13, for example the battery 102 of the [Fig.1] or of the [Fig.3].

[0069] The threshold voltage VTH is associated with a given program which will be executed for example by the processor 118. If the processor 118 is configured to execute several programs, each program has for example an associated threshold voltage which can vary from one to the other depending on the consumption required by the execution of the program.

[0070] During a step 400 (“VTH ESTIMATION”), before the execution of a program, the threshold voltage VTH associated with the program is estimated. The threshold voltage VTH depends on the power consumption required by the program execution so that the voltage of battery 102 VBAT remains above the limit voltage VLIM after the program has been executed. The estimation of the threshold voltage VTH takes into account, for example, the equivalent resistance of battery 102 and the electrical current used during program execution to estimate the charge that will be consumed during execution. For example, if the rechargeable battery 102 has a resistance If the equivalent resistance is 1 ohm and the program requires 200 mA, then program execution will consume 200 mV, and VTH will, for example, be chosen to be equal to the sum of VLIM and 200 mV so that the battery voltage remains higher than VLIM after program execution. According to one embodiment, instead of estimating the threshold voltage VTH associated with the program, the value of the threshold voltage VTH is, for example, stored in non-volatile memory 132 during the manufacture of the device 100 or subsequently by a user.

[0071] In a step 404 (“VBAT MEASUREMENT”), the voltage VBAT of the battery 102 is measured by the voltage measurement circuit 318 and is transmitted for example to the circuit 13 via the connection terminals 116 and 139. The circuit 13 compares the value VBAT to the threshold voltage VTH.

[0072] If the voltage VBAT is greater than the threshold voltage VTH (output "VBAT>VTH" of block 404), the battery is considered sufficiently charged for program execution, and circuit 13 is configured, for example, to transmit the order to processor 118 to execute the program (block 408, "RUN PROCESS"). To execute a new program, the process restarts at step 400, which estimates a new threshold voltage.

[0073] If the voltage VBAT is lower than the voltage VTH (output "VBATcVTH" of block 404), the battery 102 is considered insufficiently charged for program execution, and an alert signal is emitted, for example, by circuit 13. Depending on the value of VBAT, a second, less energy-intensive program can, for example, be executed using the remaining battery charge. Circuit 13 is configured, for example, so that the process returns to block 400 and a new threshold voltage associated with the second program is estimated.

[0074] In parallel with the battery voltage monitoring method 102 illustrated in [Fig.4], the voltage VBAT is compared to the voltage VLIM by the voltage comparator 112 of the circuit 11, as described previously in connection with Figures 1 to 3. If the voltage VBAT becomes lower than the voltage VLIM, the voltage NRST changes from the first state to the second state and the circuit 13 emits, for example, an alert signal to notify a user that a battery recharge is required.

[0075] Although in the example of [Fig.4] there is a step 400 of estimating the threshold voltage VTH, in other embodiments this step can be replaced by a step of generating the threshold voltage VTH on the basis of a control signal or a pre-calculated value stored in memory.

[0076] Fig. 5 is a graph representing an example of the evolution of the voltage VBAT, the voltage NRST and a voltage PWR_0N of the device 100 of figures 1 and 3, according to one embodiment.

[0077] The voltage PWR_0N is a voltage representative of the supply voltage of the processor 118 or the output voltage of the voltage regulator 106. For example, PWR_ON=0V when the circuit 11 is off and PWR_0N=VDDIO when the circuit 11 is on. In the example in [Fig. 5], the circuit 11 is on at time t1 and the voltage PWR_0N changes from 0V to the voltage VDDIO.

[0078] In the example of [Fig. 5], the voltage VBAT of battery 102 is higher than the limit voltage VLIM. The voltage VBAT decreases, for example, depending on the activity of circuit 11. For example, a program is executed by circuit 11 at time t2, which causes current consumption by device 100 and a decrease in the voltage VBAT.

[0079] In the example in [Fig. 5], the voltage VBAT remains greater than VLIM. As a result, the voltage NRST remains in the same state, for example the high state, and the processor 118 of the circuit 11 continues to execute the program.

[0080] Fig. 6 is a graph representing another example of the evolution of the VBAT, NRST and PWR_ON voltages of device 100 in Figures 1 and 3, according to one embodiment.

[0081] As in the example in [Fig. 5], circuit 11 is switched on at time t1 and the The voltage PWR_ON changes from 0V to the voltage VDDIO.

[0082] In the example in [Fig. 6], a program is executed at time t2, for example, current is drawn by device 100, and the voltage VBAT falls below the limiting voltage VLIM. The voltage NRST transitions from the first state to the second state at time t3, where t3 is offset from time t2 by a delay introduced by circuit 11. In the example in [Fig. 6], the voltage NRST transitions from the high state to the low state. Circuit 11 then enters the reset state; its clock signal is, for example, stopped until the voltage VBAT is sufficiently high for the voltage NRST to transition back from the second state to the first state. The processor 118 of circuit 11 stops the program execution at time t3. Furthermore, the change in the state of the NRST voltage at the connection terminal 114 triggers, for example, the emission of the warning signal by the circuit 13 so that the rechargeable battery 102 is recharged by the user.

[0083] In certain cases where comparator 112 exhibits hysteresis, when processor 118 of circuit 11 stops program execution, the current consumption of device 100 decreases and voltage VBAT rises again above VLIM but remains below the second limit voltage of voltage comparator 112. Voltage NRST remains in the second state.

[0084] One advantage of the described embodiments is that a battery charge level check can be performed without adding either a voltage comparator or an analog-to-digital converter to the circuit 13 comprising the memory non-volatile 132. Circuit 13 can therefore remain relatively compact, which is particularly advantageous in the case where circuit 13 is a host circuit of a connected object.

[0085] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to those skilled in the art. In particular, although an example including a voltage divider has been described, in other embodiments this divider is omitted, the voltage VBAT of battery 102 being, for example, compared directly with the limiting voltage VLIM.

[0086] Furthermore, although in [Fig.3] the device 100 includes a low dropout voltage regulator 106, in other embodiments other types of voltage regulator could be used, for example a switched-mode power supply (SMPS).

[0087] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Demands

1. Device for monitoring the charge level of a battery comprising: - a rechargeable battery (102); - a first circuit (11) comprising a processor (118) and a voltage comparator (112) configured to compare the voltage of the rechargeable battery (VBAT) to a limit voltage (VLIM); and - a second circuit (13), connected to the first circuit (11), comprising a non-volatile memory (132) and configured to initialize the processor (118) of the first circuit if the voltage of the rechargeable battery (VBAT) is greater than the limit voltage (VLIM).

2. Device according to claim 1, wherein the memory (132) of the second circuit (13) is a flash memory.

3. Device according to any one of claims 1 to 2, further comprising a voltage regulator (106) configured to supply voltage to the first and second circuits.

4. Device according to any one of claims 1 to 3, wherein the first circuit (11) comprises a connection terminal (114) connected to a connection terminal (134) of the second circuit (13), a signal present at the connection terminal (114) of the first circuit (11) being either in a first state or in a second state, depending on the charge level of the rechargeable battery.

5. Device according to claim 4, wherein the signal present at the connection terminal (114) of the first circuit (11) is in the second state if the battery voltage (VBAT) is less than the limit voltage (VLIM).

6. Device according to claim 4 or 5, wherein the second circuit is configured to reset the processor (118) and / or generate an alert signal if the signal present at the connection terminal (114) of the first circuit (11) is in the second state.

7. Device according to any one of claims 4 to 6, wherein the voltage of the connection terminal (114) of the first circuit (11) in the first state is greater than the voltage of the connection terminal (114) of the first circuit (11) in the second state.

8. A device according to any one of claims 1 to 7, wherein the first circuit (11) further comprises an analog-to-digital converter (318) configured to generate a value digital representation of the rechargeable battery voltage (102).

9. Device according to any one of claims 1 to 8, wherein the rechargeable battery (102) is a lithium battery.

10. A method for monitoring the charge level of a battery comprising: - comparing, by a first circuit (11), a voltage (VBAT) of a rechargeable battery (102) with a limit voltage (VLIM); and - initializing a processor (118) of the first circuit (11), by a second circuit (13) comprising a non-volatile memory (132), if the voltage of the rechargeable battery (VBAT) is greater than the limit voltage (VLIM).

11. A method according to claim 10, also comprising, before the execution of a program by the processor (118), comparing the voltage of the rechargeable battery (VBAT) to a threshold voltage (VTH), and executing the program only if the voltage of the rechargeable battery (VBAT) is greater than the threshold voltage (VTH).

12. A method according to claim 10 or 11, also comprising resetting the processor (118) and / or emitting an alert signal by the second circuit (13) if the voltage of the rechargeable battery (VBAT) is less than the limit voltage (VLIM).

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