According to a blog post by STMicroelectronics, "The LIS2DTW12 is the first Micro-Electro-Mechanical System (MEMS) in the industry to embark both an accelerometer and an absolute thermometer."
The post goes on to explain that many MEMS devices have built-in temperature sensing, but that they generally provide relative temperature based on indirect methods of comparing voltages. The LIS2D2DTW12, on the other hand, purports to allow much more accurate temperature measurement without requiring the use of a second device.
The LIS2D2DTW12, announced yesterday, provides temperature sensing accuracy of 0.8°C, while the accelerometer offers user-selectable full-scale range up to ±16g. The device offers a 50nA power-down mode as well as multiple operating modes drawing as little as 1µA or less.
Image from STMicroelectronics
This package is designed for use in space-constrained applications power conservation is critical.
This may include sensing and detection in many industries:
- Tracking and monitoring
- Gesture recognition and tap/double-tap recognition
- Motion-activated functions and user interfaces
- Display orientation detection
- Portable healthcare devices, such as hearing aids
- Wireless sensor nodes
The LIS2D2DTW12 has four user-selectable full acceleration measuring scales: ±2g/±4g/±8g/±16g. 16-bit output rates can range from 1.6 Hz to 1600 Hz. There are a total of 65 user modes that enable designers to control the unit’s power consumption.
It is configured to detect if the device it’s built into is in portrait or landscape orientation (4D orientation). It also has 6D orientation capability, which provides more detailed information about the device’s spatial position.
The unit offers configurable recognition between single-taps and double-taps. It can also detect freefall and motion used to tell the device when to “wakeup” from a sleeping/low power mode.
Temperature sensing is accomplished with output data rates (ODRs) ranging from 50 to 1.6 Hz and resolution from 8 to 12 bits.
To enhance the overall speed of system operation, the unit has an integrated 32-level first-in, first-out (FIFO) buffer. This allows the LIS2D2DTW12 to store data internally in order to limit intervention by the host processor.
Communication is accomplished through an SPI (Serial Peripheral Interface) or an I2C (inter-integrated circuit) interface.
Block diagram of the LIS2D2DTW12. Image from the datasheet.
Important Physical Considerations
Here are some additional specs. The LIS2D2DTW12:
- Is packaged in an ultra-small 2.0mm x 2.0mm x 0.7mm LGA-12 plastic land grid array package
- As a note, this is the same packaging as the device's cousin, the LIS2DW12 MEMS 3-axis accelerometer released in early 2017.
- Operates over a temperature range of -40°C to +85°C
- Belongs to the STMicroelectronics’ “femto” family, a robust, mature manufacturing process already used for the production of micromachined accelerometers
- Can operate from a power supply voltage ranging from 1.62 V to 3.6 V
- Can survive a 10,000 shock
- Complies with the ECOPACK and RoHS environmental standards
The STEVAL-MKI190V1 evaluation board is available from STMicro to allow quick testing for possible incorporation of the LIS2D2DTW12 into new product designs.
The STEVAL-MKI190V1 evaluation board. Image from STMicroelectronics
The Competitive Field
A quick scan will reveal that, while there are multiple manufacturers offering MEMS accelerometer ICs, STMicro’s claim that this is the only IC on the market that can also provide temperature readout seems justified.
In the blog post on the new component, STMicro reveals they accomplished this feat through careful calibration techniques and tighter control on the manufacturing process. Significantly, there was no penalty in regard to either needed board real estate or power to achieve a new level of temperature sensing accuracy that they claim "is extremely close to a discreet thermometer."
With this in mind, it’s unlikely the LIS2D2DTW12 will be alone for long.
Which MEMS accelerometers have you worked with in the past? What applications have you utilized them for? Let us know in the comments below.