# US 10,481,246 B2 · Photo-diode emulator circuit for transimpedance amplifier testing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,481,246 B2 - Document ID: US10481246B2 - Status: Granted - Kind: B2 - Application number: 15/934,138 - Filed: 2018-03-23 - Published: 2018-11-22 - Granted: 2019-11-19 - Earliest claimed: 2017-05-22 - Assignees: Analog Devices Global Unlimited Company - Applicants: Analog Devices Global Unlimited Company - Inventors: Devrim Aksin; Yalcin Alper Eken - Web page: https://patentgrep.com/patent/US10481246B2 ## CPC - G01S 7/497: Means for monitoring or calibrating - G01R 29/02: Measuring characteristics of individual pulses, e.g. deviation from pulse flatness, rise time or duration - G01R 31/2635: {Testing light-emitting diodes, laser diodes or photodiodes} - G01R 31/40: Testing power supplies (testing photovoltaic devices H02S50/10) - G01S 7/4816: {of receivers alone} - G01S 17/10: using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) - H03F 3/087: {with IC amplifier blocks (H03F3/085 takes precedence)} - H03K 3/0315: {Ring oscillators} - H03K 5/14: by the use of delay lines (H03K5/133 takes precedence) - H03K 2005/00058: {controlled by a digital setting} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H03F: AMPLIFIERS - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) ## Abstract Embodiments of the present disclosure provide an optical range finder that includes a transimpedance amplifier (TIA) and a photodiode emulation circuitry for testing the TIA. The photodiode emulation circuitry may be coupled to an input port of the TIA and configured to receive one or more parameters specifying one or more characteristics of a test current signal to be provided to the TIA. The photodiode emulation circuitry may further be configured to provide the test current signal in accordance with the one or more parameters to the input port of the TIA while the photodiode is also coupled to the input port of the TIA. ## Claims ### Claim 1 An optical range finder, comprising: a transimpedance amplifier (TIA); and a photodiode emulation circuitry coupled to an input port of the TIA and configured to: receive one or more parameters specifying one or more characteristics of a test current signal to be provided to the TIA, and provide the test current signal in accordance with the one or more parameters to the input port of the TIA while the photodiode is also coupled to the input port of the TIA, wherein: the test current signal includes a current pulse, the one or more characteristics include an amplitude of the current pulse, and the photodiode emulation circuitry includes a digitally controlled current mirror configured to ensure that the amplitude of the test current signal is in accordance with the one or more parameters. ### Claim 2 (depends on 1) The optical range finder according to claim 1, wherein the test current signal includes a periodic signal comprising a plurality of pulses, and wherein the one or more characteristics further include a pulse period of the plurality of pulses. ### Claim 3 (depends on 2) The optical range finder according to claim 2, wherein the photodiode emulation circuitry includes a digitally controlled oscillator configured to ensure that the pulse period of the test current signal is in accordance with the one or more parameters. ### Claim 4 (depends on 3) The optical range finder according to claim 3, wherein the digitally controlled oscillator includes a ring oscillator with a variable delay line. ### Claim 5 (depends on 4) The optical range finder according to claim 4, wherein the variable delay line is a digitally controlled delay line. ### Claim 6 (depends on 1) The optical range finder according to claim 1, wherein the one or more characteristics further include a pulse width of the current pulse. ### Claim 7 (depends on 6) The optical range finder according to claim 6, wherein the photodiode emulation circuitry includes a digitally controlled pulse generator configured to ensure that the pulse width of the test current signal is in accordance with the one or more parameters. ### Claim 8 (depends on 7) The optical range finder according to claim 7, wherein the digitally controlled oscillator includes a glitch generator with a variable delay line. ### Claim 9 (depends on 1) The optical range finder according to claim 1, wherein the one or more characteristics further include a rise time and a fall time of the current pulse. ### Claim 10 (depends on 9) The optical range finder according to claim 9, wherein the photodiode emulation circuitry includes a digitally controlled rise/fall time generator configured to ensure that the rise time and the fall time of the test current signal is in accordance with the one or more parameters. ### Claim 11 (depends on 10) The optical range finder according to claim 10, wherein the digitally controlled rise/fall time generator includes a current starving inverter. ### Claim 12 (depends on 1) The optical range finder according to claim 1, wherein the test current signal is a current signal generated in absence of optical-to-electrical conversion. ### Claim 13 (depends on 1) The optical range finder according to claim 1, wherein: the test current signal includes a current pulse, the one or more characteristics include an amplitude of the current pulse, and the photodiode emulation circuitry includes a digitally controlled current source configured to ensure that the amplitude of the test current signal is in accordance with the one or more parameters. ### Claim 14 (depends on 1) The optical range finder according to claim 1, wherein the optical range finder is a light detection and ranging (LIDAR) system. ### Claim 15 (depends on 1) The optical range finder according to claim 1, further comprising a light source and a light sensor, wherein the light source and the light sensor are configured to implement time-of-flight measurements to determine distance information to one or more objects. ### Claim 16 An optical range finder comprising: an integrated circuit (IC) device that includes a die, the die including: a transimpedance amplifier (TIA), a photodiode emulation circuitry configured to: receive one or more parameters specifying one or more characteristics of a test current signal to be provided to the TIA, generate the test current signal in accordance with the one or more parameters, and provide the test current signal to the TIA, wherein the photodiode emulation circuitry includes: a reference current generator configured to generate a reference current, a digitally controlled oscillator configured to generate a first voltage signal as a periodic signal comprising a plurality of pulses, where the one or more characteristics include a pulse period and the digitally controlled oscillator is configured to ensure that a pulse period of the first voltage signal is in accordance with the pulse period specified by the one or more parameters, a digitally controlled pulse generator configured to generate a second voltage signal based on the first voltage signal, where the one or more characteristics include a pulse width and the digitally controlled oscillator is configured to ensure that a pulse width of the second voltage signal is in accordance with the pulse width specified by the one or more parameters, a digitally controlled rise/fall time generator configured to generate a third voltage signal based on the second voltage signal and on the reference current, where the one or more characteristics include a rise time and a fall time of the plurality of pulses and the digitally controlled rise/fall time generator is configured to ensure that a rise time and a fall time of the third voltage signal is in accordance with the rise time and the fall time specified by the one or more parameters, and a current generator configured to generate the test current signal based on the third voltage signal. ### Claim 17 (depends on 16) The optical range finder according to claim 16, wherein the photodiode emulation circuitry further includes a digitally controlled mirror configured to generate a mirror output based on the reference current, and wherein the current generator is configured to generate the test current signal further based on the mirror output. ### Claim 18 (depends on 17) The optical range finder according to claim 17, wherein the photodiode emulation circuitry further includes a digitally controlled load configured to emulate a load capacitance of a photodiode while the photodiode emulation circuitry provides the test current signal to the TIA. ### Claim 19 (depends on 16) The optical range finder according to claim 16, wherein the photodiode emulation circuitry is configured to generate the test current signal without using optical-to-electrical conversion. ### Claim 20 (depends on 16) The optical range finder according to claim 16, wherein the optical range finder is a light detection and ranging (LIDAR) system. ### Claim 21 (depends on 16) The optical range finder according to claim 16, further comprising a light source and a light sensor, wherein the light source and the light sensor are configured to implement time-of-flight measurements to determine distance information to one or more objects.