US 2011/0084862 A1 · Semiconductor Integrated Circuit Device

Abstract

A high-precision A/D conversion is realized while the number of external terminals used for an A/D converter is reduced. At the time of sampling, first to fifth switches are turned on and a sixth switch is turned off. Since a first resistor is set to a resistance value optimum for sampling, an impedance in the direction from a node A to the left side and an impedance in the direction from a node B to the left side almost match, and a large noise-cancelling effect is obtained. At the time of successive approximation, the first, second, third, and fifth switches are turned off and the fourth and sixth switches are turned on. Since a second resistor is set to a resistance value optimum for the successive approximation, the impedance in the direction from the node A to the left side and the impedance in the direction from the node B to the left side almost match, and a large noise-cancelling effect is obtained also at the time of successive approximation.

Claims23

Dependent claims

A semiconductor integrated circuit device having an A/D converter of a successive approximation type that performs sampling of an input signal and successive approximation to convert an analog signal to a digital signal,

wherein the A/D converter comprises:
a first switch whose one of coupling parts is coupled to an input part to which an analog signal for A/D conversion is inputted;
a signal capacitance element whose one of coupling parts is coupled to the other coupling part of the first switch;
a D/A converter that outputs an analog signal for conversion;
a second switch coupled between an output part of the D/A converter and a coupling part between the first switch and the signal capacitance element;
a differential amplifier having a first input part to which the other coupling part of the signal capacitance element is coupled and a second input part to which one of coupling parts of a reference capacitance element is coupled, and amplifying a differential voltage;
and
an impedance matching circuit that supplies a reference voltage for comparison to the second input part of the differential amplifier via the reference capacitance element, the impedance matching circuit configured to selectively provide a first impedance or a second impedance.

5 more elements

wherein the A/D converter comprises:
a first switch whose one of coupling parts is coupled to an input part to which an analog signal for A/D conversion is input;
a D/A converter of a charge re-distribution type that samples and holds the input analog signal for A/D conversion and outputs an analog signal for conversion;
a differential amplifier having a first input part to which an output part of the D/A converter of a charge re-distribution type is coupled and a second input part to which one of coupling parts of a capacitance element is coupled, and amplifying a differential voltage;
and
an impedance matching circuit that supplies a reference voltage for comparison to the second input part of the differential amplifier via the capacitance element, the impedance matching circuit configured to selectively provide a first impedance or a second impedance.

3 more elements

a first input configured to receive a first input signal;
a signal capacitance element configured to be selectively connected to the first input;
a reference capacitance element;
a differential amplifier having a first input part connected to the signal capacitance element, a second input part connected to the reference capacitance element, and an output;
a D/A converter configured to selectively supply a converter analog signal to the first input part of the differential amplifier, via the signal capacitance element;
and
an impedance matching circuit configured to supply a reference voltage to the second input part of the differential amplifier, via the reference capacitance element;
wherein:
the impedance matching circuit is further configured to selectively provide a first impedance or a second impedance.

6 more elements

Dependencies are inferred from the claim text.

Semiconductor Integrated Circuit Device

Life of this patent

Semiconductor Integrated Circuit Device

Life of this patent

Abstract

Claims23