Circuit device and electronic apparatus

Abstract

An electronic circuit includes a noise source and an analog circuit and a logic circuit that may be adversely affected by noise. At least a portion of the analog circuit and the logic circuit is formed on a buried impurity layer whose conductivity is different from that of a substrate, and at least a portion of the periphery of that portion is surrounded by an impurity layer that is different from the substrate. Thus, propagation of the noise from the noise source is prevented.

Description

BACKGROUND[0001]1. Technical Field[0002]The present invention relates to a circuit device and an electronic apparatus or the like.[0003]2. Related Art[0004]A technique of controlling the number of revolutions of a motor by controlling a chopping current is known as a technique for a motor driver that drives a DC motor. In this technique, a current flowing to a bridge circuit is converted to a voltage by a sense resistor, and the resultant voltage is compared with a reference voltage, to detect a chopping current. The detection result is fed back to a control circuit, to perform PWM control of a drive signal for the bridge circuit, thereby rotating a motor at a fixed rate.[0005]For example, JP-A-2008-042975 discloses a technique of improving the precision of detection of the chopping current in such a motor driver. In this technique, a sense resistor is provided for each half bridge of an H-bridge, where one resistor detects that the current in the charge period has reached a predete...

AI Technical Summary

Benefits of technology

The invention aims to reduce the impact of potential fluctuations of a substrate on the operation of a circuit device. The first aspect of the invention involves forming a second circuit using a CMOS transistor on a separate layer from the first circuit, which is then isolated from the substrate by a layer. This prevents the potential fluctuations of the substrate from affecting the operation of the second circuit. The invention also allows for the supply of potential to the isolated circuit without the risk of potential fluctuations from the substrate. Additionally, the isolation of the first circuit from the substrate enables precise control and detection of its voltage or current. Overall, the invention reduces the impact of substrate potential fluctuations on circuit performance.

Problems solved by technology

Not only in a motor driver as described above, but in any circuit that performs switching operation, on / off of the current is repeated by the switching operation, and this causes a problem that the potential of a substrate fluctuates.

Images