MEMS Mic
A MEMS microphone turns sound pressure into an electrical signal using a microfabricated sensing structure and associated electronics. The capacitive designs described in the references combine a moving diaphragm with a backplate. MEMS describes the technology, not one universal interface, pinout or performance rating.
In a capacitive MEMS microphone, diaphragm motion changes capacitance. A preamplifier converts the high-impedance signal into a usable form. Analog versions provide an analog output; digital versions also perform conversion and may use PDM or I²S. PDM needs compatible filtering and decimation in the receiving system, while an I²S microphone includes the processing needed for its specified audio data format.
In plain terms
A miniature drum with an electronic ruler beside it: sound flexes a tiny diaphragm, and the sensing circuit measures the movement. The output can be an analog signal or digital data, depending on the microphone.
Why designers use it
- Provides a compact acoustic input for portable electronics.
- Offers analog and digital interface choices for different signal chains.
- Can support multi-microphone systems when timing, channel selection and processing are designed together.
Best for
- Portable audio capture
- Digital microphone interfaces
- Multi-microphone systems
Key specifications
- Output format: Analog, PDM or I²S, depending on model (Match the actual interface and clock requirements.)
- Acoustic performance: Check sensitivity, noise and overload (Use the exact datasheet and its measurement conditions.)
- Acoustic port: Top or bottom, depending on package (Use the manufacturer's recommended PCB and enclosure opening.)
When not to use it
- When the chosen microphone's acoustic noise, overload, bandwidth or environmental limits do not meet the application.
- When the processor cannot receive its output format or supply the required clocks.
- When the enclosure and PCB cannot provide the specified acoustic path.
Common mistakes
- Blocking the acoustic port or ignoring whether it faces the top or bottom of the package.
- Treating PDM and I²S as interchangeable data formats.
- Ignoring analog input loading, supply decoupling or digital clock/data integrity.
- Assuming digital output means the microphone still works outside its supply and timing limits.
Where you will find it
- Analog Devices' AN-1323 documents two ADMP421 microphones connected to an ADAU1761 codec. They share a PDM data line and clock, with opposite channel selections; the design also specifies local bypass capacitors.
- The design-considerations article describes an analog MEMS microphone feeding a non-inverting amplifier and an I²S microphone feeding a compatible processor. These are different interface choices, not interchangeable wiring recipes.
A short history
The 2009 Acoustics Today review traces silicon-microphone research through the 1980s and early 1990s, including work by Gerhard Sessler and collaborators. It identifies Knowles' SiSonic surface-mount microphone, released in 2003, as the first commercialization of MEMS microphones. This is a historical account, not evidence of today's shipment totals or the microphone fitted to every consumer product.
Good to know
- The MEMS sensing structure and its readout ASIC can be separate dies inside the same microphone package.
- Two compatible PDM microphones can share a data line by using different clock edges. Channel selection and receiver configuration still matter.
- A tiny acoustic hole is a functional part of the package. Covering it is not like covering an ordinary IC.