Advantages of Multiple Power Modes in MEMS Microphones and Sensors | Symmetry Blog

Dec 4, 2018
 

Written by Tyler Wojciechowicz
Applications Engineer at Symmetry Electronics

 

All products strive for greater performance with minimal energy consumption, but perhaps this balance between the two is under no greater scrutiny than in the Internet of Things. Many IoT ecosystems rely on a dispersed network of connected “things,” and this network is often accomplished through many small & portable devices scattered across an area.

Driving more performance with less energy can be tricky, and oftentimes trying to accomplish both at the same time can result in having the best of neither. Luckily, there is a way.

Designing an application that can switch between performance and energy saving can make all the difference. While developing such a function can be very difficult, many manufacturers have already refined this function for you, making it easy to create an application that pushes the boundaries of IoT.

Keep reading to learn more about adding multiple power modes to an application.

 

What does it mean to have multiple power modes?

If the MEMS microphone has multiple power modes, it is typically a low-power microphone intended for very low-power applications. Simply changing the clock speed changes the power mode. Low Power Mode (LPM) enables the ICS‐41350 to be used in an AlwaysOn listening mode for keyword spotting and ambient sound analysis. The ICS‐41350 will enter LPM when the frequency of SCK is between 400 and 800 kHz. In this mode, the microphone consumes only 185 µA while retaining high electro‐acoustic performance.

A common example is a smartwatch. While the LED screen of the watch face is off, the smart watch turns off or reduces the activity of many of its features. However, certain features are kept on, albeit in low power, for quick responsiveness and to stay connected to the greater Internet of Things.

 

What are the advantages of multiple power modes in MEMS microphones?

Having multiple power modes allow MEMS devices to save power while also offer better performance. The ability to switch power modes means that the devices does not have to compromise between energy consumption and performance.

 

How are these different modes selected?

A MEMS device can have multiple power modes to accommodate different situations: Standard Mode, High Performance, Low Power (AlwaysOn), and Sleep mode.

MCU selects which mode to run. This is done by modifying the microphone’s clock speed. As the clock speed decreases, so the does the performance of the microphone. Less energy is then used, allowing the microphone to save more power.

 

How does one get multiple power modes on MEMS devices?

InvenSense offers multiple power modes on many of their popular MEMS devices.

Their most notable product for this feature is the ICS‐41350, a bottom port PDM low power Multi-Mode Microphone with High AOP Mode. The ICS-41350 has multiple modes of operation: High Performance, Low Power (AlwaysOn), Standard and Sleep.

The ICS‐41350 is a low‐power, low‐noise digital MEMS microphone in a small package. The ICS‐41350consists of a MEMS microphone element and an impedance converter amplifier followed by a fourth‐order Σ‐Δ modulator. The pulse density modulated (PDM) interface allows two microphones to be time multiplexed on a data line using a single clock.

The ICS‐41350 has multiple modes of operation: High Performance, Low Power (AlwaysOn), Standard and Sleep. The ICS‐41350 has low power and high SNR in all operational modes. It has 126 dB SPL AOP in High Performance mode, and 120 dB SPL AOP in Standard and Low‐Power modes.

The ICS‐41350 supports ultrasound applications in High Performance Mode. It has an extended ultrasonic response up to 40 kHz with high SNR.

The ICS‐41350 is available in a small 3.5 × 2.65 × 0.98 mm surface‐mount package. It is reflow solder compatible with no sensitivity degradation.

 

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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