module-dual-supply

This awesome little board handles a question that persistently pops up in forums: given a voltage and ground (aka a single supply), how can you get a negative voltage (aka a dual supply)? The centerpiece of this board is the awesome little TC7660 inverting DC-DC charge pump, which can easily be sourced for less than $1 in single quantities.

This module is essentially just a breakout board for the TC7660. There are a couple of things to note when using this chip, and hence this module:

1. The positive voltage (V+) must be between 1.5V and 10V. If you need to handle higher voltages, the pin-equivalent TC7662 goes up to 15V but costs a little more than twice as much as the TC7660.

2. If, and only if, V+ is less than 3.5V then the header pin pair JP (upper-right of board layout) must be jumpered.

3. The capacitors should be 10uF. If you are using polarized capacitors, be very very sure to get the orientations correct.

4. As far as we know, the decoupling capacitor C3 is optional for the TC7660; a 2.2uF decoupling capacitor is required for the TC7662 if the input voltage has a large impedance.

5. Both the TC7660 and TC7662 can source up to 20mA, which is more than sufficient for running some dual-supply op amps on a single supply board.

6. Finally, note that the TC7660H is also available (roughly 20% for expensive than the TC7660) which has a higher switching frequency and only requires 1uF capacitors instead of 10uF capacitors.