Thermal accelerometer

Overview

Memsic's thermal accelerometers measure acceleration by sensing how a heated gas bubble moves inside a sealed cavity, so there is no solid proof mass. The sensor and its mixed-signal circuits are built on one chip in a standard CMOS process. Because there are no moving parts, Memsic says the sensors do not suffer stiction, filter out high frequency vibration, and keep a stable zero-g offset through SMT assembly.

Built for

Automotive rollover, EPB and ESC
Tilt and orientation in smart devices
Antenna and parking space monitoring
Motorcycle fall detection

Key features

No moving parts

Gas acts as the moving mass, so there is no stiction and parts pass drop testing.

High shock survival

Sensing structures are rated above 50,000 g, and the 3-axis parts above 200,000 g.

Vibration immunity

The gas behaves like a natural low-pass filter, so high frequency vibration is rejected.

Stable offset through SMT

The long thermocouple layout makes the X/Y offset tolerant of board-mount stress.

Digital and analog outputs

Parts offer I2C, SPI, PWM or analog outputs.

Automotive grades

The MXP7205VF and MXR7150VW are automotive grade 2-axis sensors for rollover and EPB.

Specifications

Technology: Thermal (gas convection) MEMS
Axes: 2 or 3, by part
Range: ±1 g to ±13.3 g, by part
Outputs: I2C, SPI, PWM or analog
Shock survival: >50,000 g (3-axis >200,000 g)
Supply: 1.8 to 5.5 V, by part
Packages: WLCSP, LGA, LCC
Grades: Consumer, industrial, automotive
Process: Standard CMOS, monolithic

Part numbers (link to datasheets)

Part	Axes	Range	Output	Package	Supply	Notes
MXC4005XC	3	±2, ±4, ±8 g	I2C, 12-bit	WLCSP 1.18 x 1.70 x 0.85 mm	1.8 to 3.6 V	Consumer grade, 6-position orientation, >200,000 g shock
MXC6655XA	3	±2, ±4, ±8 g	I2C, 12-bit	LGA 2 x 2 x 1 mm	1.8 to 3.6 V	Consumer grade, self-test, shake detection
MXC6232xG/H/M/N	2	±2 g	I2C	LCC 5 x 5 x 1.55 mm	2.7 to 3.6 V	Resolution better than 1 mg, G/H 0 to 70 °C, M/N -40 to 85 °C
MXP7205VF	2	±5 g	SPI, 800 LSB/g	LCC 5 x 5 x 2 mm	4.50 to 5.25 V	Automotive grade, 29 Hz bandwidth
MXD6235QB	2	±1 g	PWM (duty cycle)	LCC 5 x 5 x 1.55 mm	2.7 to 3.6 V	0.13 mg/√Hz noise, 0.1 mg/°C offset drift
MXC6855XU	2	±2 g	I2C, 8-bit	LCC 3 x 3 x 1 mm	2.5 to 5.5 V	4-position orientation and shake detection
MXR7150VW(-P)	2	±13.3 g	Analog, 150 mV/g	LCC 5.5 x 5.5 x 2.7 mm	4.90 to 5.25 V	Automotive grade, 29 Hz bandwidth, XZ or XY mount