What Does It Mean to Daisy Chain MEMS Microphones? | Symmetry Blog

Oct 2, 2018
 

Written by Tyler Wojciechowicz
Applications Engineer at Symmetry Electronics

 

What Does Daisy Chain Mean?

Daisy-chaining a multi-microphone configuration is an efficient and ideal method for connecting multiple microphones on the same system. A daisy changed system is superior to the traditional means of connecting multiple microphones, and if you are using multiple MEMS microphones in your device, it is important to consider a daisy chain system.

When an application needs to capture sounds across a large area, the design may call for more than one microphone. Many IoT applications fall under this requirement, as voice or sound tracking often needs to capture audio from multiple angles.

Using a standard or traditional multi-microphone configuration, each microphone must be individually connected to the MCU that handles processing of the audio data. This results in a lot of cabling and a lot of space that must be allocated for the routing of each microphone. This is especially an issue for IoT products and smaller devices, where space and efficiency can be a premium

Using a daisy chain configuration can help alleviate these issues. Rather than having each microphone individually route their digital signals to the processor, a single connection goes through all the microphones in a line. The audio signal of each microphone is sent down the line across the microphones to the MCU. Microphones built for daisy-chaining allow digital signals from other microphones to pass through uninterrupted. This creates effective and efficient signal routing from all the microphones to the MCU without the need of multiple routing or multiple ports on the MCU.

Please note that this configuration only works for digital microphones. Analog microphones transmitting analog signals will still need to use a traditional method of connecting the audio to a processor.

 

How do daisy chaining microphones work?

Microphones that possess a TDM interface are able to be daisy-chained. While the TDM interface itself has been around for a while, it has only recently been applied to microphone applications. Because a TDM interface is not standard on most MEMS microphones, it is important to look for microphones specifically designed with daisy-chaining in mind. InvenSense’s ICS-52000 is the product Symmetry recommends for daisy-chaining microphones together.

 

How many microphones can be daisy chained together?

The number of microphones that can be daisy-chained together often depends on the product being daisy-chained. The TDM interface on InvenSense’s ICS-52000 microphones allows an array of up to 16 microphones to connect directly to digital processors, such as DSPs and microcontrollers, without the need for an audio codec in the system. All microphones in an array sample their acoustic signals synchronously, enabling precise array processing.

 

What MEMS microphone should I get for daisy chaining?

InvenSense’s ICS‐52000 is a digital TDM output bottom port microphone. The complete ICS‐52000 solution consists of a MEMS sensor, signal conditioning, an analog‐to‐digital converter, decimation and anti‐aliasing filters, power management, and an industry standard 24‐bit TDM interface. The TDM interface allows an array of up to 16 of the ICS‐52000 microphones to connect directly to digital processors, such as DSPs and microcontrollers, without the need for an audio codec in the system. All microphones in an array sample their acoustic signals synchronously, enabling precise array processing.

The ICS‐52000 has a high SNR of 65 dBA and a wideband frequency response. The sensitivity tolerance of the ICS‐52000 is ±1 dB, which enables high‐performance microphone arrays without the need for system calibration.

The ICS‐52000 is available in a small 4 mm × 3 mm × 1 mm surface‐mount package.

 

APPLICATIONS

  • Speech Recognition Arrays
  • Smart Televisions
  • Teleconferencing Systems
  • Gaming Consoles
  • Security Systems
  • Microphone Arrays

FEATURES

  • Digital TDM Interface with High Precision 24-bit Data
  • Supports TDM arrays of up to 16 synchronouslysampled channels
  • High 65 dBA SNR
  • −26 dB FS Sensitivity
  • ±1 dB Sensitivity Tolerance
  • Wide Frequency Response from 50 Hz to 20 kHz
  • Low Current Consumption: 1.0 mA
  • High Power Supply Rejection: −89 dB FS
  • 117 dB SPL Acoustic Overload Point
  • Small 4 mm × 3 mm × 1 mm Surface-Mount Package
  • Compatible with Sn/Pb and Pb-Free Solder Processes
  • RoHS/WEEE Compliant

Find out more about the InvenSense ICS-52000 here.

 

Looking to integrate InvenSense products with your design? Our Applications Engineers offer free design and technical help for your latest designs. Contact us today!

 


 

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Why partner with Symmetry Electronics? Symmetry's technical staff is specially trained by our suppliers to provide a comprehensive level of technical support. Our in-house Applications Engineers provide free design services to help customers early in the design cycle, providing solutions to save them time, money and frustration. Contact Symmetry for more information.



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