Sensor in chip-scale package
The latest development from Sensirion is the SHTW2 humidity and temperature sensor, which was developed as a chip-scale package. This means that the finished sensor product that the customer purchases and integrates into their device is no larger than the sensor chip itself.
Sensirion opted for an existing chip that has already been used in another product more than 150 million times in the field and combined it with flip-chip packaging. This approach makes it possible to offer an extremely cost-effective and yet very reliable product. Sensirion’s innovation here is to merge this standard packaging technology with the humidity sensor chip without affecting its function.
With the SHTW2, a sensor is now available that can very easily be integrated in a wide range of applications. As any other component, it can be processed with standard SMD production processes and with its dimensions of 1.3x0.7x0.5mm, it can also be used in applications in which there is very limited available space.
The SHTW2 operates with a supply voltage of 1.8 V and has a fully optimized ASIC design which, among other things, results in extremely low energy consumption. The sensor needs just 1 ms to power up from from stand-by mode and perform a measurement.
At one measurement per second, which is sufficient for nearly all applications, the average power consumption is just 8.6 µW. With a lower measurement rate, this value can be significantly reduced even further. This makes the humidity and temperature sensor ideally suited for mobile applications. In addition to portable devices in the consumer electronics sector, wearable applications are also of great interest here.
The idea of using sensors directly on the human body is not new. Heart-rate measurement during sport – originally more of a medical application – is widespread, even among recreational athletes.
With the development of high-performance environmental sensors, many other new applications will become possible. The SHTW2 can, for example, be implemented in headphones to detect whether or not they are currently being worn by the user. Playback or noise cancellation can then be interrupted if the user takes off the headphones.
This is achieved by integrating two humidity and temperature sensors in the headphones. One of these is directed towards the ear, the other to the outside. Since the ear has a higher humidity than the ambient air, one sensor measures a higher value if the headphones are being worn. Using the two sensor values in combination with a corresponding algorithm, it is possible to reliably detect when headphones are put on and taken off.
The small size of the SHTW2 makes this application possible even in very small in-ear headphones and enables smarter battery management that corresponds to the individual use of battery-operated devices, such as headphones, fitness trackers, VR glasses, etc. Sensirion’s developer website (developer.sensirion.com) offers tutorials for these application examples for the creation of a prototype as well as source code for developing the algorithms.