Circuit, and waveform sensor
A circuit including a first circuit, a second circuit and a controller is provided, the first circuit and the second circuit each including a sample-and-hold circuit configured to hold a level of an input signal of a specific timing and an analog-to-digital converter circuit configured to convert the level of the input signal held in the sample-and-hold circuit into digital data and to output the digital data, the controller being configured to cause the first circuit to output the level of the input signal of a first timing and to cause the second circuit to output the level of the input signal of a second timing.
1 . A circuit comprising:
a first circuit and a second circuit each comprising a sample-and-hold circuit configured to hold a level of an input signal of a specific timing and an analog-to-digital converter circuit configured to convert the level of the input signal held in the sample-and-hold circuit into digital data and to output the digital data, wherein the input signal is a sinusoidal signal detected by an antenna coil corresponding to a column of a waveform sensor; and
a controller configured to cause the first circuit to output the level of the input signal of a first timing and to cause the second circuit to output the level of the input signal of a second timing.
2 . The circuit according to claim 1 ,
wherein the first circuit and the second circuit each comprises:
a first terminal configured to receive the input signal; and
a second terminal configured to receive a reference signal changing at a constant slope, and
wherein the analog-to-digital converter circuit acquires a counter value from a period at which a voltage of the reference signal changes to a period at which the input signal crosses with the reference signal.
3 . The circuit according to claim 2 , comprising:
a multiply-add calculator circuit configured to select the reference signal out of a first reference signal changing at a constant positive slope and a second reference signal changing at a constant negative slop, based on a polarity value of a difference between an amplitude of the input signal of the first timing and an amplitude of the input signal of the second timing, and configured to accumulate a value obtained by multiplying a value of the difference by the polarity value.
4 . The circuit according to claim 3 ,
wherein the first reference signal crosses with the second reference signal at a specific timing, and
wherein the multiply-add calculator circuit accumulates multiplication of the polarity value and a value obtained by subtracting a calibration value that is analog-to-digital-converted result in a state in which the input signal is at a ground state from the value of the difference.
5 . The circuit according to claim 1 ,
wherein the sample-and-hold circuit comprises a first capacitance and a second capacitance, and when sampling of the input signal is completed at the first capacitance, the sample-and-hold circuit separates the first capacitance from the input signal, performs conversion of the input signal into digital data, and samples the input signal at the second capacitance.
6 . A waveform sensor comprising:
a first circuit and a second circuit each comprising an input section configured to receive an input signal changing along with elapse of time, a sample-and-hold circuit configured to hold a level of the input signal of a specific timing, and an analog-to-digital converter circuit configured to convert the level of the input signal held in the sample-and-hold circuit into digital data and to output the digital data, wherein the input signal is a sinusoidal signal detected by an antenna coil corresponding to a column of the waveform sensor; and
a controller configured to cause the first circuit to output the level of the input signal of a first timing and to cause the second circuit to output the level of the input signal of a second timing.