ANALOG-TO-DIGITAL CONVERTER AND SOLID-STATE IMAGING DEVICE

摘要

To obtain accurate digital data while using a successive approximation system when performing analog-to-digital conversion processing in a plurality of steps, an AD converter includes: a signal generation unit that generates a ramp voltage based on a count signal; a signal conversion unit including a circuit that holds an input signal voltage, a successive approximation capacitance group that outputs bias voltages according to a connection combination of capacitances having different capacitance values, and a unit that compares one of the ramp voltage and the bias voltage with the signal voltage; and a control unit generating a digital signal of the signal voltage based on a comparison result of the bias voltage and the comparison result of the ramp voltage while acquiring data for calibration of the capacitance group based on the connection combination and the ramp voltage.

主权项

1. An analog-to-digital converter comprising:
a counter that counts clock signals in a predetermined direction and outputs a count signal; a ramp waveform signal generation unit that generates a ramp waveform signal based on the count signal; a plurality of signal conversion units; and a control unit that controls the signal conversion unit, wherein each of the signal conversion units includes a sample-and-hold circuit that samples a voltage of an input signal and holds the sampled voltage, a successive approximation capacitance group that has a predetermined number of capacitances having different capacitance values that successively increase by a factor of two, and outputs bias voltages having different levels by changing connection of the capacitances, a voltage addition unit that outputs an addition voltage obtained by adding a voltage selected out of a voltage of the ramp waveform signal and the bias voltage and one of the voltage held by the sample-and-hold circuit and a predetermined referential voltage, and a comparison unit that compares a voltage not to be added serving as the other of the voltage held by the sample-and-hold circuit and the predetermined referential voltage and the addition voltage, and the control unit digitally converts the voltage held by the sample-and-hold circuit based on first digital data generated based on a result obtained by the comparison unit comparing, in a connection combination of the predetermined number of capacitances, the addition voltage obtained by the addition in the voltage addition unit with the bias voltage as the selected voltage with the voltage not to be added and second digital data generated based on a result obtained by the comparison unit comparing the addition voltage obtained by the addition in the voltage addition unit with the voltage of the ramp waveform signal as the selected voltage with the voltage not to be added while acquiring data for calibration of the successive approximation capacitance group based on the connection combination of the capacitances in the successive approximation capacitance group and the signal generated by the ramp waveform signal generation unit.