DESCRIPTION

The SC1652 is a high performance inverting DC-DC converter, designed to drive an external power switch to generate programmable negative voltages. In the particularly suitable LCD bias contrast application, efficiency of 87 can be achieved with low cost PNP bipolar transistor drivers. The output voltage can be scaled to -40V by two external resistors. A pulse frequency modulation scheme is employed to maintain high efficiency conversion under wide input voltage ranges. Quiescent current is about 80μA and can be reduced to 0.7μA in shutdown mode. With a switching frequency range of 70kHz to 160kHz, small size switching components may be used, which is ideal for battery powered portable equipment such as notebook and palmtop computers.

FEATURES

? 2.4V to 7V input voltage operation

? Adjustable output voltage up to -40V

? Low quiescent current at 80μA

? Pulse frequency modulation maintains high

efficiency (max 87)

? 70kHz to 160kHz switching frequency

? Power-saving shutdown mode (0.7μA typical)

? High efficiency with low cost external PNP bipolar

transistor

APPLICATIONS

? Negative LCD Contrast Bias for

1. Notebook & palmtop computers

2. Pen-based data systems

3. Portable data collection terminals

4. Personal digital assistants

? Negative voltage supplies