7660 Negative Voltage Converter

The 7660 is a negative voltage converter IC that converts positive voltage to negative voltage, and generating a negative rail from positive voltage is very easy using this chip. The circuit shown will convert a positive voltage in the range of +1.5 V to +10 V, into a corresponding negative voltage in the same range -1.5 V to -10 V.

The application circuit for this chip is very simple and requires just two electrolytic capacitors of 10 µF value, making it ideal when a negative DC voltage is required.

For example, if the supply voltage Vcc at Pin 8 was +5 V, then the corresponding output on Pin 5 will be -5 V.

Boost function

The boost function enables a higher switching frequency of the internal oscillator. It is optional and used on applications where noise is a major consideration of the design feature.

Many different manufacturers make this 7660 chip; however, the Intersil brand has a wider input voltage range of +1.5 V to +12 V, whilst the rest operate between +1.5 V to +10 V. The Holtek and Intersil brands have a "BOOST" function on Pin 1, however on the rest, this pin is not usually used.

Circuit

Here is an example positive to negative converter circuit that will work for any voltage between +1.5 V and +10 V, to produce a corresponding negative voltage. These chips are usually used to drive low current digital and analogue circuits that require a negative voltage rail.

The IC consumes a very low supply current of around 200 µA, and the power dissipation is typically around 1.4 W, whilst the voltage conversion efficiency is approximately 97 %. As well as the standard DIP package, it is available in an SO-8 package.

Equivalent Chips