# US 9,438,262 B1 · Method for testing differential analog-to-digital converter and system therefor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,262 B1 - Document ID: US9438262B1 - Status: Granted - Kind: B1 - Application number: 14/745,653 - Filed: 2015-06-22 - Granted: 2016-09-06 - Earliest claimed: 2015-06-22 - Assignees: Freescale Semiconductor, Inc. - Applicants: Freescale Semiconductor, Inc. - Inventors: Tao Chen; Douglas A. Garrity; Xiankun Jin - Web page: https://patentgrep.com/patent/US9438262B1 ## CPC - H03M 1/109: {for DC performance, i.e. static testing (H03M1/1085 takes precedence)} - H03H 19/004: {Switched capacitor networks} - H03M 1/12: Analogue/digital converters ({H03M1/001 – } H03M1/10 take precedence) - 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) - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract A method and circuit for testing an analog-to-digital converter (ADC) are provided. The method comprises: coupling a single-ended output of an analog signal source to a differential input of an amplifier; coupling a differential output of the amplifier to a differential input of the ADC; alternately providing first and second test signals from the single-ended output of the analog signal source to first and second input terminals of the differential input of the amplifier; amplifying the first and second test signals to generate amplified differential signals at the differential output of the amplifier; providing the amplified differential signals to the differential input of the ADC; and determining if an output of the ADC is as expected. An offset may also be provided to the differential output of the amplifier. The method allows an ADC having a differential input to be tested using a digital-to-analog converter (DAC) having a single-ended output. ## Claims ### Claim 1 A method for testing an analog-to-digital converter (ADC), the method comprising: coupling a single-ended output of an analog signal source to a differential input of an amplifier; coupling a differential output of the amplifier to a differential input of the ADC; alternately providing first and second test signals from the single-ended output of the analog signal source to first and second input terminals of the differential input of the amplifier; amplifying the first and second test signals to generate amplified differential signals at the differential output of the amplifier; providing the amplified differential signals to the differential input of the ADC; and determining if an output of the ADC is as expected. ### Claim 2 (depends on 1) The method of claim 1, wherein determining if an output of the ADC is as expected further comprises determining that one or more of an integral non-linearity, differential non-linearity, offset error, and a gain error of the output of the ADC is within a predetermined criteria. ### Claim 3 (depends on 1) The method of claim 1, further comprising coupling an offset voltage to the differential output of the amplifier after the step of alternately providing the first and second test signals to first and second input terminals of the differential input of the amplifier. ### Claim 4 (depends on 3) The method of claim 3, wherein coupling the offset voltage further comprises: providing a first offset voltage to a first output terminal of the differential output of the amplifier; and providing a second offset voltage different from the first offset voltage to a second terminal of the differential output. ### Claim 5 (depends on 1) The method of claim 1, wherein the analog signal source and the ADC are both implemented on a single integrated circuit. ### Claim 6 (depends on 1) The method of claim 1, wherein alternately providing first and second test signals further comprises providing a ramped voltage to the differential input of the amplifier. ### Claim 7 (depends on 1) The method of claim 1, wherein the analog signal source is a digital-to-analog converter (DAC). ### Claim 8 (depends on 1) The method of claim 1, wherein alternately providing first and second test signals further comprises coupling a common mode voltage to the first and second input terminals of the differential input of the amplifier concurrently with the alternately providing the first and second test signals. ### Claim 9 (depends on 1) The method of claim 1, wherein the first and second test signals mimic a full rail differential analog signal. ### Claim 10 A method for testing an analog-to-digital converter (ADC), the method comprising: coupling an output of an analog signal source to a differential input of an amplifier; coupling a differential output of the amplifier to a differential input of the ADC; providing a test signal from the output of the analog signal source to the differential input of the amplifier; coupling an offset voltage to the differential output of the amplifier; amplifying the test signal to generate an amplified and offset differential signal at the differential output of the amplifier; providing the amplified and offset differential signal to the differential input of the ADC; and determining if an output of the ADC is as expected. ### Claim 11 (depends on 10) The method of claim 10, wherein the output of the analog signal source is characterized as being a single-ended output. ### Claim 12 (depends on 10) The method of claim 10, wherein the analog signal source and the ADC are both implemented on a single integrated circuit. ### Claim 13 (depends on 10) The method of claim 10, wherein providing a test signal from the output of the analog signal source to the differential input of the amplifier further comprises alternately providing first and second test signals from the single-ended output of the analog signal source to first and second input terminals of the differential input of the amplifier. ### Claim 14 (depends on 13) The method of claim 13, wherein providing first and second test signals further comprises providing a series of test codes to a digital-to-analog converter (DAC) as the analog signal source. ### Claim 15 (depends on 13) The method of claim 13, further comprising providing a common mode voltage to the differential input of the amplifier while alternately providing the first and second test signals. ### Claim 16 A differential amplifier stage comprising: a single-ended input for being coupled to a single-ended output of a digital-to-analog converter (DAC); a first switch having a first terminal coupled to the single-ended input, and a second terminal; a first capacitor having a first terminal coupled to the second terminal of the first switch, and a second terminal; a second switch having a first terminal coupled to the single-ended input, and a second terminal; a second capacitor having a first terminal coupled to the second terminal of the second switch, and a second terminal; and a differential amplifier having a first differential input coupled to the second terminal of the first capacitor, and a second differential input coupled to the second terminal of the second capacitor. ### Claim 17 (depends on 16) The differential amplifier stage of claim 16, wherein the differential amplifier is characterized as being a unity gain amplifier. ### Claim 18 (depends on 16) The differential amplifier stage of claim 16, wherein the differential amplifier further comprises a differential output. ### Claim 19 (depends on 18) The differential amplifier stage of claim 18, wherein the differential output of the differential amplifier stage is for providing a test signal to a differential input of an analog-to-digital converter (ADC). ### Claim 20 (depends on 19) The differential amplifier stage of claim 19, wherein a differential test signal for testing the ADC is generated using the first and second switches and the single-ended output of the DAC.