3-axis accelerometer (MEMS accelerometer IC)

01

Set range, sensitivity, noise and data rate

Bosch Sensortec's BMA400 datasheet describes a 12-bit digital triaxial acceleration sensor with selectable ±2, ±4, ±8 or ±16 g ranges and sensitivities of 1,024, 512, 256 and 128 LSB/g. It lists output noise density of 180 µg/√Hz on X and Y and 240 µg/√Hz on Z in high-performance normal mode, zero-g offset of 50 mg with 1 mg/K drift, sensitivity drift of 0.025 %/K, 0.5 %FS nonlinearity, 2 % cross-axis sensitivity and 0.5° alignment error. Output data rate is 12.5–800 Hz in normal mode (25 Hz in low-power mode), with a selectable 3 dB bandwidth of 0.24 or 0.48 × ODR. [1]

Minimum and maximum values are given as ±3σ over lifetime, operating temperature and voltage ranges unless stated otherwise. [1]

Editorial calculation: at ±2 g, 1,024 LSB/g is about 0.98 mg per count. RMS noise ≈ noise density × √bandwidth, so at 100 Hz ODR with 0.48 × ODR bandwidth (48 Hz), 180 µg/√Hz gives about 180 × √48 ≈ 1.25 mg rms on X and Y. [1]

A vibration-oriented part shows the other end of the range. Kionix's KX132-1211 (ROHM group, Rev. 4.0, 2021) is a ±2/4/8/16 g, 16-bit tri-axis accelerometer with output data rates up to 25,600 Hz, a mechanical signal bandwidth of 4,200 Hz on X and Y and 2,900 Hz on Z, noise density of 130 µg/√Hz (0.7 mg RMS at 50 Hz ODR), zero-g offset of ±25 mg typical (±90 mg maximum) with 0.25 mg/°C drift, 0.5% non-linearity and 2% cross-axis sensitivity. It includes a three-stage filter and RMS engine, a 512-byte buffer and wake-up thresholds down to 3.9 mg, and operates from −40 to +105 °C in a 2 × 2 × 0.9 mm LGA-12. [3]

Give the supplier the measurement range, resolution and noise needed, output data rate and bandwidth, offset and drift tolerance, power budget by mode, required on-chip functions (FIFO, interrupts, step counting, wake-up), interface and I/O voltage, shock exposure, temperature range, package and quantity.

02

Fit power modes, interface, functions and package

The BMA400 lists total supply current of 14.5 µA in normal mode at highest performance (3.5 µA at lowest oversampling), 850 nA in low-power mode at 25 Hz and 160 nA in sleep; supplies of 1.72–3.6 V for the core and 1.2–3.6 V for I/O; wake-up from sleep in 2/ODR and power-up in 1 ms; operation from −40 to 85 °C; and a 10,000 g mechanical shock rating for durations up to 200 µs. [1]

It offers SPI (4- or 3-wire) and I²C interfaces with two interrupt pins, a 1 KB on-chip FIFO, auto-low-power and auto-wake-up, activity and inactivity detection, step counting (4 µA overall), activity recognition, orientation and tap detection, in a 12-pin LGA of 2 × 2 × 0.95 mm, RoHS-compliant and halogen-free; listed uses include step counting, wearables, drop detection, window and door monitoring and coin-cell IoT devices. [1] [2]

The KX132-1211 lists 148 µA in high-performance mode at 400 Hz ODR and 0.53 µA typical (0.67 µA maximum) in low-power wake-up mode at 0.781 Hz, on a 1.7–3.6 V supply with 1.2–3.6 V I/O, SPI to 10 MHz and I²C to 3.4 MHz; it survives 5,000 g for 0.5 ms or 10,000 g for 0.2 ms. [3]

Editorial note: battery life depends on the time spent in each mode, so estimate average current from your duty cycle across normal, low-power and sleep modes. [1]

An industrial part shows the trade-off in the other direction. Murata's SCA3300-D01 product page lists a 3-axis capacitive 3D-MEMS accelerometer with user-selectable ±1.5, ±3 or ±6 g ranges, 10 or 70 Hz amplitude response, ±15 mg offset temperature characteristic, an SPI digital interface, a −40 to +125 °C operating range and a 3.0–3.6 V supply at 1 mA current consumption, in a 7.6 × 8.6 × 3.3 mm package with self-diagnostics and mechanical over-damping. Murata names levelling, tilt compensation, IMUs for heavy machinery and automotive ADAS, and navigation as target uses. Editorial calculation: 1 mA is about 69 times the BMA400's 14.5 µA normal-mode current (1,000 ÷ 14.5). [4]

Editorial calculation: at 148 µA a 220 mAh coin cell would last about 62 days running the KX132-1211 continuously at 400 Hz (220 ÷ 0.148 ÷ 24), against years in its sub-µA wake-up mode; the sampling plan, not the sensor alone, sets battery life. [3]

03

Compare what suppliers offer

The companies in the manufacturer list below show this product on their own websites. Confirm the legal seller, factory and scope for your order.

Ask each supplier for the datasheet values of noise, offset and drift at your range and data rate, current in each mode, shock rating and package, and the driver or software support for on-chip functions. [1]

04

Trace what each block controls

This is a functional reference built from the sources cited; it is not a full specification.

05

Fill the specification fields with values for your design

An accelerometer quotation needs values for your design. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

06

Send the signal, power and board data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Range/resolution: [g; mg]
Noise/rate: [µg/√Hz; Hz]
Offset/drift: [mg; mg/K]
Power: [µA by mode]
Functions: [FIFO; interrupts; step]
Interface: [SPI; I²C; VDDIO]
Shock/temp/package: [g; °C; mm]
Quantity: [units]

See manufacturer records Send an enquiry through CNFX