The SC1650 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, maximum efficiency of 90% can be achieved with low cost PNP bipolar transistor drivers. The 4V to 24V input operation range allows the SC1650 to be powered directly by the battery pack in most batteryoperated applications for greater efficiency. 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 100A and can be reduced to 8A in shutdown mode. With a switching frequency range of 100kHz to 320kHz, small size switching components may be used, which is ideal for battery powered portable equipment such as notebook and palmtop computers.