CMOS Voltage Converter

The TL7660 is a CMOS switched-capacitor voltage converter that perform supply-voltage conversions from positive to negative. With only two noncritical external capacitors needed for the charge pump and charge reservoir functions, an input voltage within the range from 1.5 V to 10 V is converted to a complementary negative output voltage of -1.5 V to -10 V. The device can also be connected as a voltage doubler to generate output voltages up to 18.6 V with a 10-V input.

The basic building blocks of the IC include a linear regulator, an RC oscillator, a voltage-level translator, and four power MOS switches. To ensure latch-up-free operation, the circuitry automatically senses the most negative voltage in the device and ensures that the N-channel switch source-substrate junctions are not forward biased. The oscillator frequency runs at a nominal 10 kHz (for VCC = 5 V), but that frequency can be decreased by adding an external capacitor to the oscillator (OSC) terminal or increased by overdriving OSC with an external clock.

For low-voltage operation (VIN < 3.5 V), LV should be tied to GND to bypass the internal series regulator. Above 3.5 V, LV should be left floating to prevent device latchup.

The TL7660C is characterized for operation over a free-air temperature range of -40°C to 85°C. The TL7660I is characterized for operation over a free-air temperature range of -40°C to 125°C.