Variable capacitor is digitally controlled

The NCD2100 electronic programmable capacitance IC has a capacitance range of 6.6 to 37.55 pF in small 63-fF steps for shunt configuration. The digitally controlled capacitance trimming setting is input via a two-wire serial bus and stored in internal nonvolatile memory. Typical applications include trimming of VCXOs and crystal oscillators, or adjusting RF stages, RFID tags, industrial wireless nodes. 

The device has tuning ratio of 5.7:1, operates from 2.5 to 5.5 V over -40° to 85°C, and comes in 2 x 2-mm DFN or 2.8 x 2.9-mm TSOT packages. It takes just 50 µA max. Approx. $0.83 ea/25,000.