How Dual-Supply Analog Switches Can Operate with a Single 3V or 5V Supply
Simply add a dual-output charge-pump voltage converter (IC1), which produces ±2VCC outputs from a single VCC input. These unregulated voltages ensure reliable switch operation for VCC levels as low as 2.5V.
Figure 1. The MAX865 dual-output charge pump (IC1) provides a local bipolar power supply for the MAX4659 CMOS analog switch (IC2).
A VCC supply voltage of 3V for the MAX865 charge pump produces ±6V rails for the switch (IC2). Using the MAX4659 CMOS analog switch results in a switch on-resistance of less than 30Ω, a transition time of less than 200ns, and low leakage current. Raising the VCC voltage to 5V generates ±10V rail supplies for the switch, reducing the on-resistance to less than 25Ω and transition times to less than 100ns. See the Typical Operating Characteristics in the MAX4659 data sheet for more information.
While the charge pump is capable of powering additional switches and/or low-power op amps, more than a few milliamps of load current degrades performance by lowering the unregulated supply rails.