1. Technical Field
The embodiments described herein relate to electronic circuits, and more particularly, to a power supply device, a processing chip for a digital microphone and related digital microphone.
2. Related Art
Digital microphone is an electro-acoustic component of the microphone, which directly outputs a digital pulse signal. Digital microphone has the characteristics of high anti-interference capabilities, high integration, and ease of use, and it is widely used for power and size sensitive portable devices.
FIG. 1 is a schematic diagram showing a digital microphone under the existing technologies. The digital microphone may include a microphone 11 and a processing chip 12. The processing chip 12 may include a power supply module 121 and a processing module 122. In particular, the microphone 11 converts the sound signals into analog electrical signals and outputs the analog signals to the processing chip 12, the processing module 122 in the processing chip 12 amplifies the analog signals and converts the amplified analog signals into digital signals for output. Under the existing technology, the power supply module 121 normally employs a low-dropout linear regulator (LDO). FIG. 2 is a circuit diagram showing the LDO under the existing technologies. The LDO may include a pass device VT, a voltage divider including R1 and R2, and an operational amplifier A. For the LDO, the power supply rejection ratio (PSRR) is an important specification. PSRR may describe the extent that the output signal is being affected by the power supply, the greater the absolute value of the PSRR, the less the output signal is being affected by the power supply.
For the processing chip 12, the higher the PSRR of the power supply module 121, the better the performance of the processing chip is, but when the power supply module 121 employs one LDO, its PSRR is still relatively low and there is no better solution for power supply module with higher PSRR under the existing technologies.