# US 11,077,755 B2 · Self-test circuit, and corresponding device, vehicle and method

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- Number: US 11,077,755 B2
- Document ID: US11077755B2
- Status: Granted
- Kind: B2
- Application number: 16/420,875
- Filed: 2019-05-23
- Published: 2019-12-05
- Granted: 2021-08-03
- Earliest claimed: 2018-05-29
- Assignees: STMicroelectronics S.r.l.
- Applicants: STMicroelectronics S.r.l.
- Inventors: Orazio Pennisi; Valerio Bendotti; Vanni Poletto
- Web page: https://patentgrep.com/patent/US11077755B2

## CPC

- G01R 31/396: Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
- B60L 3/0046: {relating to electric energy storage systems, e.g. batteries or capacitors}
- B60L 50/64: Constructional details of batteries specially adapted for electric vehicles
- G01R 31/386: {using test-loads}
- H03M 3/458: {Analogue/digital converters using delta-sigma modulation as an intermediate step}
- Y02T 10/70: Energy storage systems for electromobility, e.g. batteries
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A circuit includes a differential stage configured to provide a differential output signal. An analog-to-digital converter is coupled to first and second output nodes of the differential stage. The analog-to-digital converter is configured to provide an output signal that is a function of the differential output signal from the differential stage. A multiplexer is configured to receive a differential input signal. The multiplexer includes a test switch switchable between a conductive state and a non-conductive state. In the conductive state, the test switch couples the first input node and the second input node of the differential stage. Test signal injection circuitry is activatable to force a differential current through the differential stage. The circuit is selectively switchable between an operational mode and a self-test mode.

## Claims

### Claim 1

A circuit, comprising:
a differential stage having a first input node and a second input node, the differential stage having a first output node and a second output node configured to provide a differential output signal therebetween;
an analog-to-digital converter coupled to the first and second output nodes of the differential stage, the analog-to-digital converter configured to provide an output signal that is a function of the differential output signal from the differential stage;
a multiplexer comprising a first input terminal and a second input terminal configured to receive a differential input signal therebetween, the multiplexer also comprising a test switch switchable between a conductive state and a non-conductive state, wherein the test switch in the conductive state couples the first input node and the second input node of the differential stage; and
test signal injection circuitry activatable to force a differential current through the differential stage,
wherein the circuit is selectively switchable between an operational mode and a self-test mode,
wherein, in the operational mode, the test switch is in the non-conductive state and the multiplexer is configured to transfer the differential input signal to the first input node and the second input node of the differential stage and the test signal injection circuitry is inactive, wherein the differential output signal from the differential stage comprises a replica of the differential input signal, and
wherein, in the self-test mode, the test switch is in the conductive state and the test signal injection circuitry is active, wherein the differential output signal from the differential stage is a function of the differential current forced through the differential stage by the test signal injection circuitry.

### Claim 2 (depends on 1)

The circuit of claim 1, wherein the multiplexer is configured to couple the first input node and the second input node of the differential stage coupled in the self-test mode by the test switch in the conductive state to one of the first and second input terminals.

### Claim 3 (depends on 2)

The circuit of claim 2, wherein the multiplexer comprises a further switch switchable to a non-conductive state to decouple the first input node and the second input node of the differential stage coupled by the test switch in the conductive state in the self-test mode from the other of the first and second input terminals.

### Claim 4 (depends on 2)

The circuit of claim 2, wherein the multiplexer comprises a first switch and a second switch switchable to a conductive state to couple the first input terminal and the second input terminal of the multiplexer to the first input node and the second input node of the differential stage, respectively.

### Claim 5 (depends on 4)

The circuit of claim 4, wherein the multiplexer is selectively switchable between:
the operational mode, with the first switch and the second switch in the conductive state and the test switch in the non-conductive state; and
the self-test mode, with the test switch and one of the first and second switches in the conductive state and the other of the first and second switches in the non-conductive state.

### Claim 6 (depends on 1)

The circuit of claim 1, wherein the test signal injection circuitry is configured to selectively vary an intensity of the differential current through the differential stage.

### Claim 7 (depends on 1)

The circuit of claim 1, wherein the test signal injection circuitry comprises first and second test signal generators selectively couplable to the first input node and the second input node of the differential stage.

### Claim 8 (depends on 7)

The circuit of claim 7, wherein the differential stage comprises two differential amplifiers arranged with:
first inputs selectively couplable to the first input terminal and the second input terminal of the multiplexer, respectively; and
second inputs selectively couplable to the first and second test signal generators, respectively.

### Claim 9 (depends on 7)

The circuit of claim 7, wherein the first and second test signal generators comprise bandgap generators.

### Claim 10 (depends on 1)

The circuit of claim 1, wherein the analog-to-digital converter comprises a sigma-delta analog-to-digital converter coupled to the first and second output nodes of the differential stage, the sigma-delta analog-to-digital converter having a reference input configured to receive a reference signal and an output node, the sigma-delta analog-to-digital converter being configured to provide at its output node a bitstream having an average value that is a function of a ratio of the differential output signal from the differential stage to the reference signal.

### Claim 11 (depends on 10)

The circuit of claim 10, further comprising a digital filter coupled to the output node of the sigma-delta analog-to-digital converter to receive therefrom the bitstream and calculate the average value thereof.

### Claim 12 (depends on 10)

The circuit of claim 10, further comprising a reference signal generator that is configured to generate the reference signal and is coupled to the reference input of the sigma-delta analog-to-digital converter, wherein the reference signal generator comprises a bandgap generator.

### Claim 13 (depends on 1)

The circuit of claim 1, further comprising a differential signal source coupled to the circuit between the first input terminal and the second input terminal of the multiplexer in the circuit.

### Claim 14 (depends on 13)

The circuit of claim 13, wherein the differential signal source comprises an electrical battery cell.

### Claim 15

An electrically-propelled vehicle comprising:
an electrical battery pack including a plurality of battery cells;
a differential stage having a first input node and a second input node, the differential stage having a first output node and a second output node configured to provide a differential output signal therebetween;
an analog-to-digital converter coupled to the first and second output nodes of the differential stage, the analog-to-digital converter configured to provide an output signal that is a function of the differential output signal from the differential stage;
a multiplexer having a first input terminal and a second input terminal that is coupled to one of the battery cells of the electrical battery pack, wherein the multiplexer comprises a test switch switchable between a conductive state and a non-conductive state, wherein the test switch in the conductive state couples the first input node and the second input node of the differential stage;
test signal injection circuitry activatable to force a differential current through the differential stage;
wherein the test signal injection circuitry is selectively switchable between an operational mode and a self-test mode;
wherein, in the operational mode, the test switch is in the non-conductive state and the multiplexer is configured to transfer a differential input signal to the first input node and the second input node of the differential stage and the test signal injection circuitry is inactive, wherein the differential output signal from the differential stage comprises a replica of the differential input signal; and
wherein, in the self-test mode, the test switch is in the conductive state and the test signal injection circuitry is active, wherein the differential output signal from the differential stage is a function of the differential current forced through the differential stage by the test signal injection circuitry.

### Claim 16

A method of operating a circuit, wherein:
the circuit comprises:
a differential stage having a first input node and a second input node, the differential stage having a first output node and a second output node configured to provide a differential output signal therebetween;
an analog-to-digital converter coupled to the first and second output nodes of the differential stage, the analog-to-digital converter configured to provide an output signal that is a function of the differential output signal from the differential stage;
a multiplexer comprising a first input terminal and a second input terminal configured to receive a differential input signal therebetween, the multiplexer also comprising a test switch switchable between a conductive state and a non-conductive state, wherein the test switch in the conductive state couples the first input node and the second input node of the differential stage; and,
test signal injection circuitry activatable to force a differential current through the differential stage;
the method comprises switching the circuit between:
an operational mode, with the test switch in the non-conductive state and the multiplexer configured to transfer the differential input signal to the first input node and the second input node of the differential stage and the test signal injection circuitry is inactive, wherein the differential output signal from the differential stage comprises a replica of the differential input signal; and
a self-test mode, with the test switch in the conductive state and the test signal injection circuitry active, wherein the differential output signal from the differential stage is a function of the differential current forced through the differential stage by the test signal injection circuitry.

### Claim 17 (depends on 16)

The method of claim 16, comprising selectively varying an intensity of the differential current forced through the differential stage by the test signal injection circuitry with the circuit switched to the self-test mode.

### Claim 18 (depends on 16)

The method of claim 16, further comprising providing a bitstream having an average value that is a function of a ratio of the differential output signal from the differential stage to a reference signal.

### Claim 19 (depends on 18)

The method of claim 18, further comprising calculating an average value of the bitstream.

### Claim 20 (depends on 18)

The method of claim 18, further comprising generating the reference signal using a bandgap generator, the bitstream being output a sigma-delta analog-to-digital converter coupled to the bandgap generator.

### Claim 21 (depends on 15)

The electrically-propelled vehicle of claim 15, wherein the test signal injection circuitry is configured to selectively vary an intensity of the differential current through the differential stage.