Circuit and method for monitoring the charge level of a battery

Abstract

Circuit and method for monitoring the charge level of a battery The present 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 voltage of the rechargeable battery (VBAT) with a limit voltage; and a second circuit (13), connected to the first circuit (11), comprising a memory (132) of non-volatile type and configured to initialize the processor (118) of the first circuit if the voltage of the rechargeable battery (VBAT) is higher than the limit voltage. Figure for abstract: Fig. 3

Description

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

[0001] The present 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. Prior art

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

[0003] Monitoring the charge level of a battery generally involves measuring the voltage across the rechargeable battery, using an analog-to-digital converter (ADC), and comparing the measured voltage with a threshold. However, existing solutions are not adequate in all applications, particularly when it is desirable to have a relatively low cost and chip area. 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 is provided 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 limit 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 higher 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 comprises 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 connected to a connection terminal of the second circuit, a signal present at the connection terminal 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 lower 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 comprises 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 there is provided a method comprising: - the comparison, by a first circuit, of a voltage of a rechargeable battery with a limit voltage; and - initialization of a processor of the first circuit, by a second circuit comprising a non-volatile type memory, if the voltage of the rechargeable battery is higher than the limit voltage.

[0015] According to one embodiment, the method also comprises, 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 comprises resetting the processor and / or issuing an alert signal by the second circuit if the voltage of the rechargeable battery is lower than the limit voltage. Brief description of the drawings

[0017] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0018] [Fig.l] schematically represents 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.l], according to an embodiment of the present application;

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

[0021] [Fig.4] is a flowchart showing 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 of [Fig.3], according to one embodiment; and

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

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

[0025] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of 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", "upper", "lower", 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 "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0028] [Fig.l] schematically represents 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 illustrated in [Fig.l]), 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 the circuits 11 with voltage via the via a connection terminal 110 of the first circuit 11. The battery 102 supplies the circuit 13 with voltage 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 the circuit 13. The voltage VBAT is, for example, between 0V and 6V and, for example, between 0V and 4.5V depending on the charge level of the battery. The output voltage of the voltage regulator is, for example, between 0V and 4V and, for example, between 0V and 2V, depending on the set voltage of the voltage regulator 106 and / or the charge level of the battery 102. The output voltage of the regulator is connected to a connection terminal 130 of the circuit 13.

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

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

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

[0034] According to one embodiment, the output voltage of the 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 the comparator 112 is in the first state if VBAT is greater than the second limit voltage and the output voltage of the comparator 112 is in the second state if VBAT is less than the voltage VLIM. The output voltage of the comparator 112 remains unchanged if VBAT is between the two limit voltages. This embodiment uses hysteresis to prevent oscillation of the output signal of the comparator 112 when VBAT is close to the trip point of the comparator (in English, “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, denoted “NRST”, is indicative of the state of charge of battery 102.

[0038] When the voltage VBAT becomes lower 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 drops below a minimum level for the proper operation of the circuit 11. In addition, 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 choices of the low voltage state for the second state and of powering the comparator 112 with the voltage VBAT ensure that, if the voltage VBAT decreases below the threshold of the limit voltage VLIM, then the voltage NRST will naturally decrease towards the low voltage state, indicative of a low level of the battery 102.

[0040] The second circuit 13 comprises a non-volatile memory 132 (MEM), used when starting the device 100.

[0041] The circuit 13 comprises a connection terminal 134 connected to the connection terminal 114 of the circuit 11. The circuit 13 is for example configured to evaluate the charge level of the battery 102 by reading the voltage NRST at the terminal 134. According to one embodiment, if NRST is in the second state then the battery is not sufficiently recharged and the circuit 13 emits an alert signal, for example to the user of the 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 comprises for example a connection terminal 138 connected to the ground rail 104 of the device 100 and comprises 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 the circuit 11 so that the circuit 13 can communicate with the processor 118. The 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 for transmitting data from the circuit 13 to the circuit 11 and a MISO (Master Input, Slave Output) data line for transmitting 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 of the directions, multiplying by that much the communication speed between the circuits.

[0044] According to one embodiment, the circuit 11 does not comprise a non-volatile memory and comprises, for example, a volatile memory, for example of the random access memory 140 (RAM). The initialization of the processor 118 is carried out by the circuit 13 and, for example, by loading a binary code into the RAM memory 140. For example, a binary code recorded in the memory 132 of the circuit 13 is loaded into the RAM memory 140 when the processor 118 starts. The processor 118 is, for example, configured to read the binary code and execute it.

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

[0047] In a step 200 of the method (“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 recorded in the non-volatile memory 132 of [Fig.l],

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

[0049] If terminal 134 is in the first state (output “YES” of block 202), this means that voltage VBAT is greater than VLIM and that the battery is sufficiently recharged to start 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 the circuit 11 of [Fig. 1]. The code is for example transmitted via an interface, for example a data bus, between the connection terminals 139 and 116 and for example according to an SDIO or SPI protocol. The transmitted code makes it possible for example to initialize the processor 118 of the circuit 11 which does not include for example 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] schematically represents in block form the device 100 of [Fig. 1] in more detail.

[0053] Some elements of [Fig.3] are identical to elements of [Fig.l]. 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 included in 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 greater 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 voltage ALIM. When VBAT is less than ALIM, the voltage regulator 106 is configured to generate a voltage which follows the evolution of the voltage VBAT.

[0058] The voltage VBAT at terminal 110 of the circuit 11 is for example divided by a voltage divider bridge 311, for example composed of two resistors connected in series between terminal 110 and the ground rail 104, an intermediate node between the resistors providing the divided voltage. The divided voltage is compared to the limit voltage VLIM by the comparator 112 (“VBAT Monitor”). The voltage at the output of the 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 the comparator 112 is connected for example to an input of an OR logic gate 314. The logic gate 314 comprises for example other inputs connected to fault detection circuits (not illustrated in [Fig.3]) present in the circuit 11 and which are in the first state in the event 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 recharged.

[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 connection terminal 114 and to a first 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 connection terminal 310. Electrode 316 is a pull-up resistor and makes it possible to reduce conduction between connection terminal 310 and ground rail 104 when transistor 315 is activated.

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

[0063] The arrangement of transistor 315 makes it possible to maintain the second state at terminal 114 even if the battery voltage VBAT falls below a minimum level for the proper operation of circuit 11. In addition, transistor 315 makes it possible to maintain the first state at terminal 114 as long as the battery voltage VBAT remains above the minimum level for the proper operation of circuit 11, and otherwise, to switch to the second state. The choices of the low voltage state for the second state and of supplying terminal 114 with the voltage VBAT ensure that, if the voltage VBAT decreases below the threshold of the limit voltage VLIM, then the voltage NRST will naturally decrease towards the low voltage state, indicative of a low level of battery 102.If the processor 118 of the circuit 11 is switched off, the other inputs of the logic gate 314 are for example fixed at the low voltage level and only the input corresponding to the voltage level 312 of the battery 102 can vary. The voltage NRST 114 therefore remains indicative of the voltage level of the battery VBAT before switching on the processor 118 of the circuit 11.

[0064] The drain of transistor 315 is for example also connected to 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 the circuit 11 is for example connected to a module 317 of the circuit 11. The module 317 is for example connected to a connection terminal 119 of the circuit 11 which is for example connected to the ground rail 104 of the device 100. The module 317 is for example connected to the terminal 110 to be powered by the voltage VBAT and is for example configured to execute functions of the device 100, for example the establishment of wireless communication with an external device not shown in [Fig. 3]. The module 317 comprises 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, the circuit 11 measures the value of the voltage VBAT via the voltage measuring circuit 318 and transmits the value of VBAT to the circuit 13 via the connection terminals 116 and 139. The circuit 11 is for example configured to be able to operate in different operating regimes, for example a regime consuming less energy if the voltage VBAT is lower than a fixed voltage, higher than the limit voltage VLIM, for example 3V. Depending on the value of VBAT, the circuit 13 is for example configured to control the operating regime of the 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 in order to verify that the voltage VBAT is above this threshold. The threshold voltage VTH corresponds for example to a minimum voltage for the correct execution of the program. The optional consideration of the threshold voltage VTH will now be described in relation to [Fig.4].

[0068] [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 [Fig.1] or [Fig.3].

[0069] The threshold voltage VTH is associated with a given program which will for example be executed 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 with respect to one another 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 for example estimated. The threshold voltage VTH depends on the consumption requested by the execution of the program so that the voltage of the battery 102 VBAT remains higher than the limit voltage VLIM following the execution of this program. The estimation of the threshold voltage VTH takes into account for example the equivalent resistance of the battery 102 and the electric current used during the execution of the program to estimate the charge which will be consumed during the execution. For example, if the rechargeable battery 102 has a resistance equivalent of 1 ohm and the program requires 200mA, then the execution of the program will consume 200mV and VTH will for example be chosen equal to the sum of VLIM and 200mV so that the battery voltage remains higher than VLIM after the execution of the program. 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 recorded in the 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 for example transmitted to the circuit 13 via the connection terminals 116 and 139. The circuit 13 compares the value VBAT with the threshold voltage VTH.

[0072] If the voltage VBAT is higher than the threshold voltage VTH (output “VBAT>VTH” of block 404), it is considered that the battery is sufficiently recharged for the execution of the program and the circuit 13 is for example configured to transmit the order to the processor 118 to execute the program (block 408, “RUN PROCESS”). To execute a new program, the process resumes at step 400 of estimating a new threshold voltage.

[0073] If the voltage VBAT is lower than the voltage VTH (output “VBATcVTH” of the block 404), it is considered that the battery 102 is not sufficiently recharged for the execution of the program and an alert signal is for example emitted by the circuit 13. Depending on the value of VBAT, a second program, less energy-consuming, can for example be executed with the remaining charge level of the battery. The circuit 13 is for example configured so that the method returns to the block 400 and a new threshold voltage associated with the second program is estimated.

[0074] In parallel with the method for monitoring the voltage of the battery 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 FIGS. 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 signal to a user that recharging of the battery 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 precalculated value stored in memory.

[0076] [Fig. 5] is a graph representing an example of the evolution of the VBAT voltage, the NRST voltage and a PWR_0N voltage of the device 100 of FIGS. 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 of the output voltage of the voltage regulator 106. For example, PWR_ON=OV when the circuit 11 is off and PWR_0N=VDDI0 when the circuit 11 is on. In the example of [Fig.5], the circuit 11 is on at time t1 and the voltage PWR_0N goes from 0V to the voltage VDDIO.

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

[0079] In the example of [Fig.5], the voltage VBAT remains higher 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 the device 100 of FIGS. 1 and 3, according to one embodiment.

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

[0082] In the example of [Fig. 6], a program is for example executed at time t2, a current is consumed by the device 100 and the voltage VBAT decreases below the limit voltage VLIM. The voltage NRST changes from the first state to the second state at a time t3, where t3 is offset relative to time t2 by a delay introduced by the circuit 11. In the example of [Fig. 6], the voltage NRST changes from the high state to the low state. The circuit 11 then enters the reset state, its clock signal is for example stopped until the voltage VBAT is high enough for the voltage NRST to change back from the second state to the first state. The processor 118 of the circuit 11 stops the execution of the program at time t3. In addition, the change of state of the NRST voltage at the connection terminal 114 triggers, for example, the emission of the alert signal by the circuit 13 so that the rechargeable battery 102 is recharged by the user.

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

[0084] An advantage of the described embodiments is that a check of the charge level of a battery can be carried out without adding either a voltage comparator or an analog-to-digital converter in the circuit 13 comprising the memory. non-volatile 132. The circuit 13 can therefore remain relatively compact, which is particularly advantageous in the case where the 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 occur to those skilled in the art. In particular, although an example comprising a voltage divider bridge has been described, in other embodiments this divider bridge is omitted, the voltage VBAT of the battery 102 being for example compared directly with the limit voltage VLIM.

[0086] Furthermore, although in [Fig. 3] the device 100 comprises 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 those skilled in the art from the functional indications given above.

Claims

Claims

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) with a limit voltage (VLIM); and - a second circuit (13), connected to the first circuit (11), comprising a memory (132) of non-volatile type and configured to initialize the processor (118) of the first circuit if the voltage of the rechargeable battery (VBAT) is higher than the limit voltage (VLIM).

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

3. A 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 lower 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. A 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 higher 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 representative of the voltage of the rechargeable battery (102).

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

10. 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 memory (132) of non-volatile type, if the voltage of the rechargeable battery (VBAT) is higher than the limit voltage (VLIM).

11. The method of claim 10, further comprising, prior to 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, further comprising resetting the processor (118) and / or issuing an alert signal by the second circuit (13) if the voltage of the rechargeable battery (VBAT) is lower than the limit voltage (VLIM).

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