Smart capacitive sensing enables optimisation for speed
ams has released a new configurable capacitive sensing front end named the PCap04, which gives sensor manufacturers the ability to balance speed and resolution to match their design requirements. When optimised for speed, the PCap04 can capture and digitise up to 50,000 sensor measurements per second. When sampling at a slower rate to optimise for precision, the PCap04 can achieve a measurement resolution of 8aF.
The configurability of the device also enables sensor manufacturers to trade measurement speed off against power consumption.
In low power mode, the PCap04 draws a current as low as 4.0µA. ams has developed a demonstration board with no external power supply, in which the PCap04 operates on the energy harvested from the RF field generated by an NFC reader such as a smartphone.
The PCap04 IC is intended for use with any sensing element that generates a change in capacitance. Featuring six capacitance measurement channels, it is well suited to use with sensing elements which measure parameters such as pressure, force, position, tilt, humidity, weight, level and many others.
The PCap04’s output may be supplied as a PWM or PDM representation of the raw measured capacitance value.
The device also features a DSP to process the sensor measurements and convert them into digital values transmitted via an I2C or SPI interface. It can handle input capacitance values over a broad range from as little as 1pF to as much as 100nF.
The PCap04 provides various built-in configuration options, including support for grounded, floating, differential and differential grounded sensor connections.
The DSP can run ams open-source code as well as user-generated code for functions such as measurement linearisation and conversion. ams provides an evaluation kit and a user-friendly software development tool which make it easy for the design engineer to develop, test and debug code to run on the PCap04.
“The PCap04 gives sensor manufacturers a flexible alternative to other sensor front ends on the market today that have have fixed operating characteristics. It offers the unique advantage of enabling sensor manufacturers to fine-tune the operation of the sensor front end to meet the requirements of their specific application,” said Georg Jedelhauser, Marketing Director at ams.
The PCap04 is available now in production volumes. It is supplied as a bare die, or housed in a QFN-24 plastic package.
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