Abstract: A Class D amplifier module includes a semiconductor chip and n inductors. The semiconductor chip includes n output stages, n high-side drivers, and n low-side drivers. The semiconductor chip and the n inductors are housed in a single package and operate according to a control signal received from an external processor.

Abstract: A power-on reset circuit is provided to a semiconductor device including a first power supply pin and N (N?1) second power supply pins. A voltage monitoring circuit is configured with a voltage at the first power supply pin as its power supply, and compares each of the voltages supplied to the N second power supply pins with a corresponding threshold value. When the supplied voltage exceeds the corresponding threshold value for all the second power supply pins, the voltage monitoring circuit asserts a trigger signal TRIG. A reset signal generating circuit is configured with the voltage at the first power supply pin as its power supply. The reset signal generating circuit asserts a reset signal POR_OUT in response to assertion of the trigger signal TRIG.

Abstract: An audio amplifier includes an operational amplifier, a replica of an output stage of the operational amplifier, and a feedback circuit configured such that, in a normal mode, an output signal of the operational amplifier is fed back to the input side of the operational amplifier, and such that, in a calibration mode, an output signal of the replica is fed back to the input side of the operational amplifier. The calibration circuit cancels out the offset voltage of the audio amplifier. An adjustment circuit changes the offset of the audio amplifier according to a control signal S1. A control circuit adjusts the control signal such that an output signal VS of the replica is within a predetermined target range in a state in which a predetermined voltage is input to the audio amplifier. Memory stores the control signal S2 acquired in the final stage.

Abstract: A power-on reset circuit is provided to a semiconductor device including a first power supply pin and N (N?1) second power supply pins. A voltage monitoring circuit is configured with a voltage at the first power supply pin as its power supply, and compares each of the voltages supplied to the N second power supply pins with a corresponding threshold value. When the supplied voltage exceeds the corresponding threshold value for all the second power supply pins, the voltage monitoring circuit asserts a trigger signal TRIG. A reset signal generating circuit is configured with the voltage at the first power supply pin as its power supply. The reset signal generating circuit asserts a reset signal POR_OUT in response to assertion of the trigger signal TRIG.

Abstract: A bias circuit supplies a bias voltage VBIAS to a microphone. A variable gain amplifier amplifies a reference voltage VREF. A low-pass filter removes a high-frequency component from the output of the variable gain amplifier. A voltage follower amplifier receives the output voltage of the low-pass filter, and supplies the output voltage to the microphone.

Abstract: An audio amplifier includes an operational amplifier, a replica of an output stage of the operational amplifier, and a feedback circuit configured such that, in a normal mode, an output signal of the operational amplifier is fed back to the input side of the operational amplifier, and such that, in a calibration mode, an output signal of the replica is fed back to the input side of the operational amplifier. The calibration circuit cancels out the offset voltage of the audio amplifier. An adjustment circuit changes the offset of the audio amplifier according to a control signal S1. A control circuit adjusts the control signal such that an output signal VS of the replica is within a predetermined target range in a state in which a predetermined voltage is input to the audio amplifier. Memory stores the control signal S2 acquired in the final stage.

Abstract: A bias circuit supplies a bias voltage VBIAS to a microphone. A variable gain amplifier amplifies a reference voltage VREF. A low-pass filter removes a high-frequency component from the output of the variable gain amplifier. A voltage follower amplifier receives the output voltage of the low-pass filter, and supplies the output voltage to the microphone.