EP1315061A1 - Power controller for an electronic circuit, component and device therefor - Google Patents

Abstract

A comparator (45) activates a RESET signal, when compared voltage proportional to supply voltage is lower than reference voltage. A preliminary circuit outputs immediate reference voltage (V09) less than principal reference voltage (VBGAP) supplied by a bandgap module. A control circuit receives a reference voltages and activates RESET signal, until principal reference voltage reaches predetermined threshold. <??>An Independent claim is also included for electronic device.

Description

The field of the invention is that of electronic circuits. More specifically, the invention relates to the electrical supply of such circuits, and in particular the control of the supply voltage delivered.

Micro-electronic circuits are designed to operate at a given nominal supply voltage (for example VCC = 5 V). They can of course operate within a predetermined voltage range, around this nominal value. However, their proper functioning cannot be guaranteed in outside this range. For example, a memory powered at a voltage too weak (for example VCCMIN = 2.55 V) could have a random behavior, inducing unwanted read and / or write operations.

It is therefore necessary to monitor the circuit supply, and only authorize its operation when the supply voltage is within the desired range (for example VCC> 2.55 V). So the circuit does not work only when it is actually capable of operating without making an error. In below this minimum supply voltage, the circuit is forced into re-initialization (RESET).

This is the role of the power controller.

In known manner, to know precisely the supply voltage vcc delivered to a circuit, we generally compare part of this voltage VCC, at the output of a voltage reference module, according to the principle illustrated in figure 1.

The “bangdap” module 11 is a module based on pnp transistors, which delivers a precise reference voltage Vref (for example Vref = 1.25 V). A resistive bridge 12, formed of two resistors R1 and R2 (worth for example each 100 kΩ) delivers a fraction of VCC (in the example described: VCC / 2). These two voltages are directed to a comparator 13, which issues a command for RESET as soon as VCC / 2 ≤ Vref. We therefore obtain a "RESET" as soon as VCC / 2 ≤ 2.5 V.

A disadvantage of this technique is that, if it proves effective for slow feed rises, however it does not work in the case of rapid feed rises. Indeed, in this case, the module output "bandgap" can remain at 0V when the supply voltage VCC has already reached, for example, 2 V. Comparator 13 therefore releases the RESET command, although that the supply voltage has not yet reached the desired nominal value.

To overcome this problem, we thought of adding an RC circuit to the controller. 21 on the supply voltage VCC, as illustrated in FIG. 2. This RC circuit allows to force the RESET command for fast climbs, in waiting for the device in Figure 1 to take over.

However, this technique is not 100% reliable. Depends on supply rise slope, VCC supply voltage level, temperature and / or technology used, it happens that the RC 21 circuit releases RESET control while the part of the detector of figure 1 does not not work yet.

In addition, this technique is not suitable for circuits using a fine technology (0.35 µm for example) which does not support feeding greater than a determined threshold (for example 4 V).

So, if we consider a circuit that must be able to operate with a battery voltage (VBAT) between 2.5 V and 5.5 V, while the technology does not support more than 4 V, we insert a regulator internally (at from a "bandgap" module), which will supply the rest of the circuit with 3 V. however, all the elements connected to VBAT must be made with transistors supporting 5.5 V. They will therefore use a thicker, wider oxide (for example 0.6 µm) and less efficient. This is particularly the case for the module "bandgap" and 3V regulator.

This implies that the "bandgap" module only works from a minimum voltage of 2.4 V, for example, whereas with 3V transistors it would have operated from 1.6 V. With such a device, in the case of a slow rise of power up to 2.3 V, RC circuit 21 releases RESET command while the "bandgap" module is always at 0 V, since it receives a voltage lower (2.3 V) than its minimum operating voltage (2.4 V).

Again, the comparator 12 releases the RESET command (since it sees VCC / 2 = 1.15 V> 0 V), while the supply voltage VCC has not reaches 2.55 V.

In addition, according to this technique, it is not possible to control voltages less than 2.4 V, because the "bandgap" module no longer works.

The invention particularly aims to overcome these drawbacks of the state art.

More specifically, one objective is to provide a power controller for electronic circuit, which works efficiently and reliably to prevent circuit operation as long as the supply voltage has not reached a threshold value, in all conditions, and in particular that the climbs feed are slow or fast.

Another object of the invention is to provide such a controller power supply, which is simple, inexpensive and easy to produce and implement. In particular, an objective of the invention is to provide such a controller, of which all of the constituents can be produced using the same technology, and especially a technology finish.

The invention also aims to provide such a controller power supply that can work at low voltages, compared to art previous (and for example less than 2.4 V).

These objectives, as well as others which will appear below, are achieved at using a power supply controller of an electronic circuit, delivering a supply voltage (VCC) and preventing operation of said circuit, at using a RESET signal, when said supply voltage is less than a first predetermined threshold, said controller comprising a first comparator (C2) comparing a voltage proportional to said voltage supply to a reference voltage and activating said reset signal, when said voltage proportional to said supply voltage is lower at said reference voltage, and a “bandgap” module delivering a voltage of main reference (VBGAP).

According to the invention, the controller comprises reference means preliminary, immediately delivering a preliminary reference voltage (V09), lower than said main reference voltage, but not very precise, and control means receiving said preliminary reference voltage (V09) and the main reference voltage (VBGAP), and systematically activating said reset signal (RESET) as long as said main reference voltage (VBGAP) has not reached a second predetermined threshold.

Thus, as long as the main reference voltage is not available, that the feed rise is slow or fast, we have the means to guarantee that the RESET command is activated, and therefore that there will be no random circuit operation due to too low supply voltage.

Preferably, said control means comprise means for selecting a reference voltage (VREF) for said first comparator (C2), between said preliminary reference voltage (V09) and said main reference voltage (VBGAP), said preliminary reference voltage (V09) being selected as long as said main reference voltage (VBGAP) has not reached said second predetermined threshold.

The power controller also includes a module for regulation, delivering a regulated supply voltage (VCC) to said circuit, which advantageously takes account of said reference voltage (VREF).

In other words, the reference voltage is chosen from the two references available, and switched to the main reference voltage as soon as possible.

According to an advantageous aspect of the invention, said supply voltage regulated (VCC) also supplies said “bandgap” module. This allows to realize the latter in a finer technology, and make it work at lower voltages.

According to another advantageous characteristic of the invention, said means control units issue a command to said regulation means, controlling means for amplifying said regulated supply voltage (VCC) to a third predetermined threshold, as long as said main reference voltage has not not reached said first predetermined threshold.

Thus, the gain is temporarily increased, as long as the voltage is used. preliminary reference, to take into account the fact that it is weaker and to obtain despite this, an acceptable supply voltage.

According to a preferred embodiment, said reference means preliminary include a diode-mounted transistor.

Advantageously, said control means comprise a second comparator (C1) supplied by said preliminary reference voltages (V09) and main (VBGAP) and supplying an inverter (INV) driving a transistor (TP1) intended to force said reset signal (RESET).

Preferably, said selection means comprise two transistors, respectively receiving said preliminary reference voltages (V09) and main (VBGAP) and controlled respectively by the output of said second comparator (C1) and the output of said inverter (INV).

According to an advantageous characteristic, said means of regulation comprise an amplifier (AOP) delivering said supply voltage regulated (VCC) and supplied on the one hand by said reference voltage (VREF) and secondly by a divider bridge on which said regulated supply voltage (VCC) is looped back.

Preferably, said limiting means comprise a transistor mounted so as to short-circuit part of said dividing bridge. The invention also relates to electronic components and devices electronics comprising, or cooperating with, at least one controller power supply as described above.

• les figures 1 et 2, déjà commentées en préambule, présentant deux techniques connues de détection d'alimentation, respectivement sans et avec circuit RC ;
• la figure 3 est un schéma fonctionnel d'un contrôleur d'alimentation selon l'invention ;
• la figure 4 présente de façon plus détaillée un mode de réalisation du contrôle de la figure 3,
• les figures 5A à 7B illustrent différentes simulations de fonctionnement du contrôleur de la figure 4, respectivement :
  • figures 5A et 5B : montée d'alimentation rapide ;
  • figures 6A et 6B : montée d'alimentation lente ;
  • figures 7A et 7B : chute d'alimentation.

Other characteristics and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment of the invention, given by way of simple illustrative and nonlimiting example, and of the appended drawings, among which :

• FIGS. 1 and 2, already commented on in the preamble, presenting two known techniques of supply detection, respectively without and with RC circuit;
• Figure 3 is a block diagram of a power controller according to the invention;
• FIG. 4 presents in more detail an embodiment of the control of FIG. 3,
• FIGS. 5A to 7B illustrate different operating simulations of the controller of FIG. 4, respectively:
  • FIGS. 5A and 5B: rapid supply rise;
  • Figures 6A and 6B: slow feed rise;
  • Figures 7A and 7B: power drop.

FIG. 3 illustrates the general principle of the invention, in the form of a simplified block diagram.

As explained in the preamble, the main objective of a controller is to prevent the powered circuit from starting to work before that the supply voltage has reached a predetermined sufficient value. so that this is not the case, the controller issues a RESET command to the circuit 31, which forces it into re-initialization mode.

The controller according to the invention always includes a "bandgap" module 32, of known structure, designed to deliver a reference voltage main stable VBGAP. Control means 33 direct it towards a comparator C2 34, which also receives a voltage 35 representative of the circuit supply voltage. As long as the latter is lower than the voltage reference, comparator 34 provides a RESET command 31.

To overcome the drawbacks of the prior art, provision is also made for immediate reference 36, immediately delivering a preliminary reference voltage V09, which may be imprecise, but is available instantly, before the "bandgap" module is active.

The control means 33 are designed to select, as reference voltage VREF, either voltage V09, or voltage VBGAP, depending on whether the latter is or is not sufficient, for example according to the rule: VREF = MAX (V09, VBGAP). Thus, during the voltage build-up phase, we temporarily replaces VBGAP with another voltage, immediately available.

The control means 33 act directly (37) on the control 31 RESET, as long as the "bandgap" module 32 has not started.

The controller also comprises regulation means 38, which supply the supply voltage VCC (for example 3V) to the circuit. These means 38 take into account the VREF voltage to regulate the power supply.

According to a particular aspect of the invention, the "bandgap" module 32 is powered by the VCC voltage (and not, conventionally, by the battery voltage VBAT), which allows it to operate at lower voltages, and with thinner transistors.

Furthermore, the control module 33 delivers to the regulation means 38 a gain modification command 39, which acts on means 30 amplification of the regulated voltage, as long as VBGAP has not reached its value operating minimum.

We now present a particular mode of implementation of this power controller, shown in Figure 4.

The immediate reference V09 is obtained using a transistor 41 mounted diode and connected to the battery (VBAT, of the order of 2.5 V to 5.5 V), via a resistor 42, for example 1MΩ. This transistor therefore delivers a voltage V09 lower than the "bandgap" voltage, of the order of 0.9 V. It can vary by 0.6 V at 1 V depending on the technology, the supply voltage and the temperature in particular.

This preliminary reference V09 is present from the start whatever the feed rise time. It will serve as a preliminary reference to regulation means 43, for delivering the VCC voltage of 3V.

These regulation means 43 can be assimilated to a voltage multiplier by a factor of 2.4 (3 V / 1.25 V = 2.4). With the preliminary reference VREF a 0.9 V, so they generate 2.16 V. They include an operational amplifier 431, whose output delivers the voltage VCC, via a transistor 432. This output is looped back to its "minus" input via a 433 resistor of 910 kΩ.

This output voltage VCC also supplies the “bandgap” module 44. It is therefore not supplied directly by the battery voltage VBAT but, like the rest of the circuit, by VCC. He therefore sees only 3V at most. In Consequently, it can be achieved using thin oxide transistors, plus performing.

The minimum operating voltage of this new "bandgap" module is thus 1.6 V, instead of 2.4 V.

A C1 45 comparator makes it possible to compare the output of the "bandgap" module (VBGAP) and the preliminary reference V09. When the main reference VBGAP exceeds preliminary reference V09, i.e. when VCC is greater than 1.6 V and there has been enough time for the "bandgap" module 44 initializes, the reference voltage VREF is VBGAP. Beforehand, she corresponds to V09.

• directement sur le transistor 46, qui délivre V09 ;
• via un inverseur 48 sur le transistor 47, qui délivre VBGAP.

For this, the output of comparator 45 acts on two pass-transistors 46 and 47, as follows:

• directly on transistor 46, which supplies V09;
• via an inverter 48 on the transistor 47, which delivers VBGAP.

As soon as VBGAP is taken as a reference, the regulatory means 43 regulate 2.4 times VBGAP, and therefore stabilize around 3 V.

According to the invention, VREF is therefore equal at the start to V09, then to VBGAP, as soon as it exceeds V09, that is: VREF = MAX (V09, VBGAP).

VREF feeds a C2 49 comparator, which compares VREF to part of VCC, delivered by a divider bridge comprising two resistors 410 and 411 of 100 kΩ and 96 kΩ respectively. The output of comparator C2 49 acts on the RESET 412 command.

Thus, the comparator 49 releases the RESET command 412 only when VCC / 2 is greater than VREF, i.e. VCC> 2.55 V.

Additional security blocks the control of RESET 412, via a transistor 413 controlled by the inverse (PASS) of the output of comparator 45. Thus, as long as comparator 45 has not switched to voltage VBGAP, the RESET is strength.

When VREF = VBGAP, comparator 49 takes over, for whether or not to release RESET 412 depending on the VCC power level, therefore precisely.

According to a particular aspect of the invention, means are provided for modification of the multiplying factor of the regulation means 43. For this, as long as VREF = V09, the resistance 435 is short-circuited, when the output of the comparator 45 is active, that is to say that VREF = V09.

Thus, it is possible to generate a supply voltage close to 3 V as soon as possible, so as to be sure that the "bandgap" 44 module starts even if V09 is only 0.6 V (in the opposite case, i.e. in the absence of transistor 414, 0.6 V x 2.4 = 1.44 V: the "bandgap" module may not start with such a supply voltage).

The general operation of this controller is therefore as follows: during the rise of the supply voltage VBAT, the voltage V09 is present from the beginning. The regulator 43 uses it as a reference and generates approximately 3 V, the gain being compensated by transistor 414. This voltage allows the "bandgap" module 44 to start. Meanwhile, RESET 412 is forced to VCC.

When the "bandgap" module is working (therefore VBGAP> V09), the regulator 43 then uses VBGAP as a reference and generates 3 V. The comparator C1 45 releases the RESET and it is the comparator C2 49 which controls the latter and which will only release it when VCC> 2.55 V.

Figures 5A and 5B show a simulation of the different voltages VBAT, V09, VBGAP, VCC, RESET (figure 5A) and REF, PASS (figure 5B), in the case of a rapid supply rise of 10µs. (functional even at 100 ns), with VBGAP = 1.16 V instead of 1.25 V, and therefore a regulatory factor of 2.6 at instead of 2.4.

It can be seen that V09 is present quickly. The regulator is trying to generate VCC at around 3 V as soon as VBAT is sufficient for it to function. The "bandgap" module is powered by VCC and puts a little time before starting.

When VBGAP> V09, PASS allows the regulator to take as VBGAP reference instead of V09 and VCC will then be precisely regulated from "bandgap" module.

As long as VBGAP <V09 the RESET is blocked at VCC. So the circuit complete supplied with VCC remains under RESET. In this case of rapid rise, VCC> 2.55 V when the bandgap exceeds V09, and the RESET is released as soon as that PASS switches.

Then VBGAP = 1.16 V as long as VCC> 1.6 V.

We can then check supply voltages up to 1.6 V, by modifying the R1 / R2 ratio of resistors 410 and 411.

Figures 6A and 6B present a simulation of a climb slow power, 1 ms duration. V09 is present again from the start. The regulator tries to generate around 3 V but VBAT is still insufficient for it. So VCC = VBAT as long as VBAT <3 V. As soon as VCC is sufficient (around 1.5 V), the "bandgap" module 44 is working. When VBGAP> V09, the comparator C1 switches, as well as PASS, and the new regulator reference becomes VBGAP.

The RESET is then no longer controlled by the comparator C1. However, the comparator C2 compares VCC / 2 and VREF (= VBGAP) and keeps the circuit under RESET as long as VCC remains below 2.55 V.

Then, when VBAT increases beyond 3 V, the regulator 43 fills its role and precisely delivers VCC = 3 V.

Likewise, it is possible to control feed falls up to a VCC minimum for the "bandgap" module to work, ie 1.6 V, as well as illustrated by Figures 6A and 6B, which show a drop power supply with detection at 2.55 V.

Claims (12)

Power supply controller of an electronic circuit, supplying a supply voltage (VCC) and preventing the operation of said circuit, using a reset signal (RESET), when said supply voltage is lower at a first predetermined threshold,
said controller comprising a first comparator (C2) comparing a voltage proportional to said supply voltage to a reference voltage and activating said reset signal, when said voltage proportional to said supply voltage is lower than said reference voltage , and a “bandgap” module delivering a main reference voltage (VBGAP),
characterized in that it comprises preliminary reference means, immediately delivering a preliminary reference voltage (V09), lower than said main reference voltage,
and control means receiving said preliminary reference voltage (V09) and the main reference voltage (VBGAP), and systematically activating said reset signal (RESET) as long as said main reference voltage (VBGAP) has not reaches a second predetermined threshold. Power controller according to claim 1, characterized in that said control means comprise means for selecting a reference voltage (VREF) for said first comparator (C2), between said preliminary reference voltage (V09) and said main reference voltage (VBGAP),
said preliminary reference voltage (V09) being selected as long as said main reference voltage (VBGAP) has not reached said second predetermined threshold. Supply controller according to claim 2, characterized in that it comprises a regulation module, delivering a regulated supply voltage (VCC) to said circuit, taking account of said reference voltage (VREF). Power controller according to claim 3, characterized in that said regulated supply voltage (VCC) powers said "bandgap" module. Power controller according to any one of claims 3 and 4, characterized in that said control means issue a command to said regulation module, controlling means for modifying a multiplier factor applied to said regulation module so as to generate said regulated supply voltage (VCC) at a third predetermined threshold, as long as said main reference voltage has not reached said first predetermined threshold. Power controller according to any one of claims 3 to 5, characterized in that said regulation module comprises an amplifier (AOP) delivering said regulated supply voltage (VCC) and supplied on the one hand by said reference voltage (VREF) and on the other hand by a divider bridge on which said regulated supply voltage (VCC) is looped back. Power controller according to claims 5 and 6, characterized in that said means for modifying a multiplier factor comprises a transistor mounted so as to short-circuit a part of said divider bridge. Power controller according to any one of Claims 1 to 7, characterized in that the said preliminary reference means comprise a transistor mounted as a diode. Supply controller according to any one of Claims 1 to 8, characterized in that the said control means comprise a second comparator (C1) supplied by the said preliminary (V09) and main (VBGAP) reference voltages and supplying an inverter ( INV) driving a transistor (TP1) provided to force said reset signal (RESET). Power controller according to claims 2 and 9, characterized in that said selection means comprise two transistors, receiving respectively said preliminary (V09) and main (VBGAP) reference voltages and controlled respectively by the output of said second comparator (C1) and the output of said inverter (INV). Electronic component characterized in that it comprises at least one power controller according to any one of claims 1 to 10. Electronic device characterized in that it comprises at least one power controller according to any one of claims 1 to 10.

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