Noise suppression technologies/case study introduction (Consumer)

Noise countermeasures for ameliorating sensor malfunction (1)

Need for sensor noise suppression

Sensors are key devices of the Internet of Things (IoT) and self-driving cars, and they are expected to be used even more in many types of equipment in the future.

However, there are also cases where serious accidents may result if sensors do not correctly transmit the sensed data.
This makes noise suppression both important and essential for various types of sensors.

This chapter investigates the malfunction mechanisms and noise suppression methods, using one-chip type sensors*1 (digital output type) as an example.

※1With the development of MEMS technology, one-chip type sensors are becoming the mainstream.

figure: Need for sensor noise suppression

Recommended noise suppression circuit for one-chip sensors

Target interface

INDEX

Target interface

I2C

Signal frequency

100kbps(50kHz)、400kbps(200kHz)、3.4Mbps(1.7MHz)etc -> Maximum approx. 2MHz

Cut-off frequency
(Signal frequency x 5)

10MHz

figure: Recommended circuit
Recommended circuit
figure: Signal line insertion loss
Signal line insertion loss
figure: Power line insertion loss
Power line insertion loss

Target interface

SPI

Signal frequency

1~2Mbps(1MHz), 20Mbps(10MHz) etc -> Maximum approx. 10MHz

Cut-off frequency (Signal frequency x 5)

50MHz

figure: Recommended circuit
Recommended circuit
figure: Signal line insertion loss
Signal line insertion loss
figure:
Power line insertion loss

In view of the above, we recommend :

Recommended noise suppression filters for one-chip sensors
The typical interfaces used by digital one-chip sensors are I2C and SPI.
The signal frequencies are not constant, but the cut-off frequencies required of filters are around 10 MHz for I2C and around 50 MHz for SPI, so the above-noted filters are suitable.

For further "problems" that can be anticipated,

We will explain the mechanisms of sensor malfunction due to noise, and the key points of countermeasures

Related articles