In summary, Silicon Labs offers a broad portfolio of capacitive sensing products with its patent-pending Capacitance to Digital Converter (CDC), including the F990. Built on the F900 low power platform, the F990 adds up to fourteen capacitive touch sensing channels and features low power capacitive sensing. When a touch is identified and the CPU becomes active, the 25 MIPS core provides excellent performance at 150µA/MHz. The on-board hardware CDC is the same patent-pending CDC which is in the F700 and F800 product families. With thirteen channels in a 20-pin package and fourteen channels in a 24-pin package, the C8051F990 is an ideal solution for lower-button count applications. The hardware CDC offers high interference immunity and a 40µS button scan time.  In addition to the 25 MIPS MCU, the device also features a high resolution ADC, voltage reference, comparator, internal oscillators, a temperature sensor, and a 6-bit current DAC to handle other application demands. There are many different techniques to measure the change in self-capacitance which is a conductive plate’s capacitance to its surroundings, the C8051F70x/71x/800/99x family uses a successive approximation technique to compare the sensor capacitor ramp with a known time base. The CS0 module conversion is capable of being generated from several sources including software trigger, all of the timers and auto-scanning. Because all of the required components for capacitive sensing are integrated on chip, the capacitive sense pad can connect directly to the MCU. Also, the C8051F99x touch sense MCUs feature sub micro amp (<1 μA) wake on touch average current consumption, 150 µA/MHz active mode and multiple sleep modes as low as 10 nA. With up to fourteen capacitive sensing inputs and a patent-pending charge timing hardware capacitance to digital converter, the C8051F99x achieves good touch sensitivity, speed and low power in packages as small as a 3 mm x 3 mm QFN20.