Analog multiplexer uses flying capacitors

摘要

This design idea describes a way to increase the number of analog inputs to your microcontroller for cases in which adding an analog-multiplexer chip or upgrading to a microcontroller with more inputs might be impractical. If the microcontroller you're using has some spare I/O pins and at least one of them is bidirectional or is amenable to trista'ting, you can configure a simple analog multiplexer using switched capacitors. Figure 1 shows a two-input multiplexer. A typical switched-capacitor multiplexer completely disconnects the capacitor from the sensed voltage before sampling the voltage across the capacitor.