Abstract:
A ramp generator for use in readout circuitry includes an integrator coupled to receive a ramp generator input reference signal to generate a reference ramp signal coupled to be received by an analog to digital converter. A power supply compensation circuit that is coupled to generate the ramp generator input reference signal includes a delay circuit including a variable resistor and a filter capacitor coupled to receive a power supply signal. The variable resistor is tuned to match a delay ripple from the power supply to a bitline output. A capacitive voltage divider is coupled to the delay circuit to generate the ramp generator input reference signal. The capacitive voltage divider includes a first variable capacitor coupled to a second variable capacitor that are tuned to provide a capacitance ratio that matches a coupling ratio from the power supply to the bitline output.
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:
A method of reducing harmonic tones of noise in an image sensor includes generating a system clock and generating a random clock in response to the system clock. A charge pump is clocked with the random clock to generate a boosted voltage. The boosted voltage is provided to a pixel array of the image sensor. Image charge is readout from pixel cells of the pixel array using the boosted voltage from the charge pump.
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.