# US 2019/0170813 A1 · Self-test circuit and a method of checking the integrity of a signal through a signal path

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- Number: US 2019/0170813 A1
- Document ID: US20190170813A1
- Status: Published application
- Kind: A1
- Application number: 15/830,046
- Filed: 2017-12-04
- Published: 2019-06-06
- Earliest claimed: 2017-12-04
- Assignees: Aktiebolaget Skf
- Applicants: Aktiebolaget SKF
- Inventors: Julian Franchitti
- Web page: https://patentgrep.com/patent/US20190170813A1

## CPC

- G01R 31/2884: {using dedicated test connectors, test elements or test circuits on the IC under test (G01R31/2855 takes precedence)}
- G01R 29/22: Measuring piezoelectric properties
- G01R 31/2829: {Testing of circuits in sensor or actuator systems (testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844)}
- G01R 31/2843: {In-circuit-testing}
- H10P 74/277: {Circuits for electrically characterising or monitoring manufacturing processes, e.g. circuits in tested chips or circuits in testing wafers}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

Examples provide for a self-test circuit. The self-test circuit comprises input circuitry; testing circuitry; and a circuit to be tested, coupled between the input and testing circuitry and comprising at least a piezoelectric crystal. The input circuitry is configured to generate and transfer a predefined electric signal comprising at least a sinusoidal signal through at least the piezoelectric crystal of the circuit to be tested to generate an output signal. The testing circuitry is configured to analyze the output signal.

## Claims

### Claim 1

A self-test circuit comprising:
input circuitry;
testing circuitry; and
a circuit to be tested coupled between the input and testing circuitry and comprising at least a piezoelectric crystal; wherein
the input circuitry is configured to generate and transfer a predefined electric signal comprising at least one sinusoidal signal through at least the piezoelectric crystal of the circuit to be tested to generate an output signal, and wherein
the testing circuitry is configured to analyze the output signal.

### Claim 2 (depends on 1)

The self-test circuit of claim 1, wherein the circuit to be tested further comprises at least one of a low-pass, bandpass, and a high-pass filter circuit, and wherein the input circuitry is configured to transfer the predefined electric signal through the piezoelectric crystal and the at least one of the low-pass, the bandpass, and the high-pass filter circuit of the circuit to be tested to generate an output signal.

### Claim 3 (depends on 1)

The self-test circuit of claim 1, wherein the testing circuitry is configured to perform signal amplitude or frequency assessments on the output signal.

### Claim 4 (depends on 1)

The self-test circuit of claim 1, wherein the testing circuitry comprises a signal processor configured to convert the output signal from time domain to frequency domain and to analyze the output signal in the frequency domain.

### Claim 5 (depends on 1)

The self-test circuit of claim 1, wherein the input circuitry is configured to generate the at least one sinusoidal signal with a frequency greater than 0 Hz and less than the resonant frequency of the piezoelectric crystal.

### Claim 6 (depends on 1)

The self-test circuit of claim 1, wherein the input circuitry comprises a digital signal processor configured to generate a predefined digital signal and to convert the digital signal to the analog domain to generate the predefined electric signal.

### Claim 7 (depends on 1)

The self-test circuit of claim 1, further comprising a switch configured to select between normal operation and test mode, wherein, when in test mode, the switch connects the input circuitry to the circuit to be tested and wherein the switch remains in test mode at least until the output signal is generated.

### Claim 8

A method for self-testing a circuit comprising:
generating a predefined electric signal;
transferring the predefined electric signal comprising at least one sinusoidal signal through at least a piezoelectric crystal of a circuit to be tested to generate an output signal; and
analyzing the output signal.

### Claim 9 (depends on 8)

The method of claim 8, further comprising transferring the predefined electric signal through the piezoelectric crystal and at least one of a low-pass, bandpass, and high-pass filter circuit of the circuit to be tested to generate an output signal.

### Claim 10 (depends on 8)

The method of claim 8, wherein analyzing the output signal comprises performing signal amplitude or frequency assessments on the output signal.