Abstract:
An example method for fast ramp start-up during analog to digital conversion (ADC) includes opening a feedback bypass switch coupled to an amplifier to initiate an ADC operation, providing an injection current pulse to an inverting input of the amplifier, where the non-inverting input is coupled to a feedback bypass switch, integrating a first reference current coupled to the inverting input of the amplifier, where the integrating of the first reference current occurs due to the opening of the feedback bypass switch, and providing a reference voltage in response to the injection current pulse, the integrating of the first reference current, and a reference voltage coupled to a non-inverting input of the amplifier, where a level of the reference voltage is increased at least at initiation of the ADC operation in response to the injection current pulse.
Abstract:
A pixel circuit includes a photodiode, and a transfer transistor coupled to the photodiode. A floating diffusion is coupled to the transfer transistor coupled to transfer image charge from the photodiode to the floating diffusion. An amplifier circuit includes an input coupled to the floating diffusion, an output coupled to generate an image data signal of the pixel circuit, and a variable bias terminal coupled to receive a variable bias signal. A reset switch is coupled between the output and input of the amplifier circuit to reset the amplifier circuit in response to a reset signal. A variable bias generator circuit is coupled to generate the variable bias signal in response to a reset signal to transition the variable bias signal from a first bias signal value to a second bias signal value in response to a transition of the reset signal from an active state to an inactive state.
Abstract:
An image sensor pixel noise measurement circuit includes a pixel array on an integrated circuit chip. The pixel array includes a plurality of pixels including a first pixel to output a first image data signal, and a second pixel to output a second image data signal. A noise amplification circuit on the integrated circuit chip is coupled to receive the first and second image data signals from the pixel array. The noise amplification circuit is coupled to output an amplified differential noise signal in response to the first and second image data signals received from the pixel array. A fast Fourier transform (FFT) analysis circuit on the integrated circuit chip is coupled to transform the amplified differential noise signal output by the noise amplification circuit from a time domain to a frequency domain to analyze a pixel noise characteristic of the pixel array.
Abstract:
An example method for fast ramp start-up during analog to digital conversion (ADC) includes opening a feedback bypass switch coupled to an amplifier to initiate an ADC operation, providing an injection current pulse to an inverting input of the amplifier, where the non-inverting input is coupled to a feedback bypass switch, integrating a first reference current coupled to the inverting input of the amplifier, where the integrating of the first reference current occurs due to the opening of the feedback bypass switch, and providing a reference voltage in response to the injection current pulse, the integrating of the first reference current, and a reference voltage coupled to a non-inverting input of the amplifier, where a level of the reference voltage is increased at least at initiation of the ADC operation in response to the injection current pulse.
Abstract:
A pixel cell includes a photodiode to accumulate image charge. A global shutter transistor is coupled to the photodiode to reset the image charge in the photodiode in response to a global shutter control signal. A global shutter control signal generator circuit generates the global shutter control signal to have a first value signal or a second value signal. The first value signal is coupled to turn on the global shutter transistor to reset the photodiode. The second value signal controls the global shutter transistor to be in a low leakage off mode. A supply circuit is coupled to provide the second value signal to the global shutter control signal generator circuit. The supply circuit includes a variable filter circuit coupled to an output of the supply circuit to selectively vary a bandwidth of the second value signal in response to a bandwidth select signal.
Abstract:
An example method for fast ramp start-up during analog to digital conversion (ADC) includes opening a feedback bypass switch coupled to an amplifier to initiate an ADC operation, providing an injection current pulse to an inverting input of the amplifier, where the non-inverting input is coupled to a feedback bypass switch, integrating a first reference current coupled to the inverting input of the amplifier, where the integrating of the first reference current occurs due to the opening of the feedback bypass switch, and providing a reference voltage in response to the injection current pulse, the integrating of the first reference current, and a reference voltage coupled to a non-inverting input of the amplifier, where a level of the reference voltage is increased at least at initiation of the ADC operation in response to the injection current pulse.
Abstract:
A pixel cell includes a photodiode disposed in a semiconductor material to accumulate image charge in response to light. A global shutter transistor is disposed in the semiconductor material and is selectively resets the image charge in the photodiode in response to a global shutter control signal. A global shutter control signal generator circuit is coupled to generate the global shutter control signal to have a first value, a second value, and a third value. The first value of the global shutter control signal is coupled to turn on the global shutter transistor to reset the photodiode. The third value of the global shutter control signal is coupled to control the global shutter transistor to be in a low leakage off mode. The second value of the global shutter control signal is between the first and third values and is turns off the global shutter transistor.
Abstract:
A readout circuit for use in an image sensor includes a sense amplifier circuit coupled to a bitline to sense analog image data from a pixel cell of the image sensor. An analog to digital converter is coupled to the sense amplifier circuit to convert the analog image data to digital image data. A ramp generator circuit is coupled to generate a first ramp signal. The analog to digital converter is coupled to generate the digital image data in response to the analog image data and the first ramp signal. A first capacitive voltage divider is coupled to the ramp generator. The first capacitive voltage divider is coupled to reduce an output voltage swing of the first ramp signal coupled to be received by the analog to digital converter to reduce noise in the first ramp signal.
Abstract:
A ramp generator includes a supply voltage sampling circuit coupled to sample a black signal supply voltage during a black signal readout, and an image signal supply voltage of the pixel cell during an image signal readout of a pixel cell. A first integrator circuit receives a buffered reference voltage, and an output of the supply voltage sampling circuit. First and second switches are coupled between the first integrator circuit and a first capacitor to transfer a signal representative of a difference between the image signal supply voltage and the black signal supply voltage to the first capacitor. A second integrator circuit is coupled to the first capacitor to generate an output ramp signal coupled to be received by an analog to digital converter. A starting value of the output ramp signal is adjusted in response to the difference between the image signal and the black signal supply voltage.
Abstract:
An example method for fast ramp start-up during analog to digital conversion (ADC) includes opening a feedback bypass switch coupled to an amplifier to initiate an ADC operation, providing an injection current pulse to an inverting input of the amplifier, where the non-inverting input is coupled to a feedback bypass switch, integrating a first reference current coupled to the inverting input of the amplifier, where the integrating of the first reference current occurs due to the opening of the feedback bypass switch, and providing a reference voltage in response to the injection current pulse, the integrating of the first reference current, and a reference voltage coupled to a non-inverting input of the amplifier, where a level of the reference voltage is increased at least at initiation of the ADC operation in response to the injection current pulse.