Fujitsu Corporation

Atsushi Hitaka

Atsushi Matsuda

Hiromi Nanba

Tatsuhiro Mizumasa

Kenichi Minobe

Masashi Okubo

Tohru Mizutani

Yoshinori Yoshikawa

A frequency detecting circuitdetects frequency of a sampling pulse SP, and outputs the detected frequency as a detection value VOUT. A current adjusting circuitadjusts a power supply current Ivd to be supplied to an AD converterin accordance with the detection value VOUT. The power supply current Ivd varies continuously so as to follow the sampling frequency. As a result, an optimum power supply current Ivd can always be supplied in accordance with the operating frequency of the AD converter. That is, power consumption of the AD convertercan be reduced. Since the power supply current Ivd can be adjusted in accordance with the sampling frequency, it is possible to form the AD converterthat has a wide frequency band and allows great versatility.

Semiconductor integrated circuit

An integrated circuit includes an analog signal output unit which converts a digital output signal into at least one analog output signal, and outputs the at least one analog output signal, an analog signal input unit which converts at least one analog input signal received from an exterior into a digital input signal, a switch circuit which provides at least one signal path through which the at least one analog output signal is supplied from the analog signal output unit to the analog signal input unit as the at least one analog input signal, and an offset adjustment control circuit which supplies an output offset from the analog signal output unit to the analog signal input unit via the at least one signal path so as to detect the digital input signal inclusive of the output offset and an input offset, and cancels offsets of the analog signal output unit and the analog signal input unit in response to the output offset and the input offset obtained from the detected digital input signal.

Digital-analog-conversion circuit having function of automatic offset adjustment

Growing community of inventors

Kawasaki, Japan

Atsushi Hitaka