Micro electro-mechanical systems (MEMS) is a field of devices that has garnered significant interest due to the industry’s fervent desire to make smaller, lower power devices.
MEMS technology, in general, tends to have some very distinct advantages, including smaller sizes, minuscule power consumption, and low cost. For this reason, the technology has found itself in a plethora of applications, including speakers, LiDAR, and more.
A comparison of different consumer MEMs microphones. Image used courtesy of System Plus Consulting
TDK is one company that has continually pushed the envelope of MEMS technology, and that is a direction it has no intention of changing. Earlier this week, TDK made MEMS headlines by releasing three brand new MEMS microphones for its SmartSound family that claims to enable higher quality and lower power performance for mobile and IoT devices.
This article will look at what MEMS microphone technology entails and then dive deeper into these three new offerings from TDK.
MEMS Microphones––How it Works
A MEMS microphone works in a manner that is very similar to that of a standard electret condenser microphone (ECM).
Standard MEMS microphone layout. Image used courtesy of CUI Devices
A MEMS microphone uses a capacitive element with a substantial impedance that exhibits changes in capacitance corresponding to the air-pressure variations that we call sound.
However, the difference between this and an electret is the transducer. In a MEMS microphone, the transducer is in the same package as the signal processing circuitry, generally on a small PCB.
Analog (left) and digital (right) MEMS microphone signal chains. Image [modified] used courtesy of Analog Devices
Inside the microphone package, the audio signal chain begins with the output of the transducer being sent to a preamplifier. The preamp converts the changing capacitance of the transducer into the analog signal, which is then used as the output in analog MEMs devices. After that, the preamp’s output is sent to an ADC for a digital MEMS microphone and sent digitally via pulse density modulation or I2S.
Now that a basic understanding of MEMs microphones has been established, looking at TDK’s three new offerings should show how it has expanded on this technology.
TDK’s New Releases
This week, TDK released three new MEMS microphones in the hopes of obtaining the smaller size, lower power consumption, and (arguably) higher audio quality offered by MEMS. Each microphone is focused on mobile and IoT areas; however, the three microphone offerings target different applications and environments.
The first offering is the T5919, a PDM digital MEMS microphone. Notably, TDK claims this is the world’s first PDM MEMS microphone with a built-in Particle Ingress Filter (PIF).
The PIF filter is a physical filter (not electrical) that protects the device from moisture and other debris in the environment, making this offering ideal for harsh environment applications.
Coming in a 3.5 x 2.65 x 0.98 mm bottom port package, the T5919 microphone maintains a 135 dB sound pressure level (SPL) acoustic overload point (AOP) in High-Quality Mode and a 120 dB SPL AOP in Low-Power mode.
Three new MEMS microphones from TDK. Image used courtesy of TDK
Following the T5919, the T3903 is also a PDM digital MEMS microphone––this one focuses on very low power operation with a wide dynamic range. According to the datasheet, in high-quality mode, this device offers sensitivity down to −37 dBV, SNR of 66 dBA, and current consumption at a minuscule 590 µA (220 µA in low power mode).
The last offering is the T4086, which is an analog output MEMS microphone optimized for space-constrained applications. Coming in a tiny 2.75 × 1.85 × 0.9 mm package outline, the T4086 offers an SNR of 62dBA, AOP of 127 dB, a sensitivity of -39 dBV, and current consumption of 140 µA.
Made for Mobile
As IoT and mobile demand lower and lower power, MEMS devices continue to grow in popularity. TDK’s newest MEMS microphones are proof of this, and the company hopes to see their latest products deployed into products in the short term future.
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