Why Review MEMS Sensors

Sensors are where the physical world meets the digital system, and their datasheets rarely tell the full story of how they behave in a product. This review examines two ST MEMS devices from the perspective of an FAE who supports customers through design-in: the LIS3DH three-axis accelerometer and the LPS22HB absolute pressure sensor. Both are measured on typical evaluation setups, with attention to accuracy, power modes, interfaces and the practical details of integration.

LIS3DH Accelerometer

The LIS3DH is an ultra-low-power three-axis accelerometer with selectable full scale of plus or minus 2, 4, 8 or 16 g and a digital output over I2C or SPI in a small 3 by 3 millimetre LGA package. Its defining feature is the combination of low current with embedded detection: free-fall, tap and 4D orientation detection, plus a FIFO buffer, let the device detect events itself and batch data so the host can sleep. For wearables and IoT nodes, that combination is often the simplest way to add motion awareness without draining the battery.

Accuracy in Practice

The accelerometer's accuracy depends mostly on the full-scale range and the output data rate. A smaller range gives finer resolution but saturates sooner, so the choice is a trade-off between resolution and headroom. For orientation and tilt, a small range is best; for shock and free-fall detection, a wider range is needed. The device is factory-calibrated, and the zero-g offset is small enough that most applications need no external calibration.

Power Modes

The device draws very little current in its low-power modes, and the embedded detection lets the host remain asleep until an event occurs. In our measurements, the current stayed low enough for continuous operation in a wearable, provided the output data rate was matched to the application rather than set to the maximum. Setting a high rate when a low rate would do is the most common way to waste power.

LPS22HB Pressure Sensor

The LPS22HB is an ultra-compact absolute pressure sensor covering 260 to 1260 hectopascals with 24-bit pressure output and 16-bit temperature output over I2C or SPI. Its current consumption is as low as 3 microamps, and it comes in a 2 by 2 millimetre package that measures just 0.76 millimetres high, which makes it small enough for portable and wearable products. Embedded temperature compensation removes the need for software compensation, and the FIFO buffer reduces host wake-ups.

Accuracy and Altitude

The 24-bit output gives fine resolution, which translates into good altitude resolution for altimeters and indoor navigation. In our bench testing, the relative accuracy across the operating range was good enough for altitude estimation without external calibration beyond the recommended one-point calibration after soldering. The absolute accuracy depends on the calibration, and the embedded compensation handles the temperature variation.

Integration

Both sensors connect over standard I2C or SPI and are supported by the STM32Cube ecosystem, so they integrate quickly with an STM32 host. The main integration tasks are the power modes and the interrupt configuration, both of which are straightforward once the application's requirements are clear. BeiLuo's FAE team supports the configuration and can supply samples for bench validation.

Verdict

The LIS3DH and LPS22HB are strong examples of why ST is a leading MEMS supplier: they combine small size, low power and embedded features that make a product easier to build and longer-lasting. For motion and environmental sensing in wearables, IoT nodes and industrial monitoring, they are a dependable starting point. Match the range and rate to the application, use the embedded features rather than polling, and validate on the bench.