Direct current (DC) correction circuit for a time of flight (TOF) photodiode front end
First Claim
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1. A system, comprising:
- a driver configured to produce a high frequency (HF) drive signal that can be used to drive a light emitting element with the HF drive signal to thereby cause a HF light signal to be emitted;
an optical sensor configured to produce a sensor signal indicative of light that is incident on the optical sensor,wherein the sensor signal includes a low frequency (LF) component and a HF component,wherein the LF component, which includes a direct current (DC) component, is indicative of ambient light that is not of interest, andwherein the HF component is indicative of reflected light that is of interest;
front end circuitry including one or more amplifiers and/or one or more filters; and
DC correction loop circuitry including a pair of transconductance amplifiers and configured to remove the LF component from the sensor signal, while passing the HF component of the sensor signal to the front end circuitry, to thereby prevent DC saturation of the front end circuitry.
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Abstract
A system and method that compensates for the effects of ambient light in a time of flight (TOF) sensor front end is provided. Moreover, a direct current (DC) correction loop is utilized at the front end, which removes a DC component from a current generated by the TOF sensor and accordingly prevents saturating the front end. The DC correction loop attenuates the DC component without adding significant thermal noise at a modulation frequency and provides a corrected signal to the front end circuitry. The corrected signal is processed and utilized to detect a position of an object within the optical field of the sensor.
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Citations
18 Claims
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1. A system, comprising:
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a driver configured to produce a high frequency (HF) drive signal that can be used to drive a light emitting element with the HF drive signal to thereby cause a HF light signal to be emitted; an optical sensor configured to produce a sensor signal indicative of light that is incident on the optical sensor, wherein the sensor signal includes a low frequency (LF) component and a HF component, wherein the LF component, which includes a direct current (DC) component, is indicative of ambient light that is not of interest, and wherein the HF component is indicative of reflected light that is of interest; front end circuitry including one or more amplifiers and/or one or more filters; and DC correction loop circuitry including a pair of transconductance amplifiers and configured to remove the LF component from the sensor signal, while passing the HF component of the sensor signal to the front end circuitry, to thereby prevent DC saturation of the front end circuitry. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A DC correction loop circuit, comprising:
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a first transconductance amplifier (gm1) including a non-inverting (+) input, an inverting input (−
) and an output; anda second transconductance amplifier (gm2) including an input coupled to an output of the first transconductance amplifier (gm1) and an output coupled to the non-inverting (+) input of the first transconductance amplifier (gm1); a capacitor coupled between the output of the first transconductance amplifier (gm1) and the inverting (−
) input of the first transconductance amplifier (gm1); anda resistor coupled between the inverting (−
) input of the first transconductance amplifier (gm1) and a reference voltage (Vref). - View Dependent Claims (14, 15, 16, 17, 18)
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Specification