DESCRIPTION
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 100µA and can be reduced to 8µA 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.

FEATURES
 • 4V to 24V input voltage operation
 • Adjustable output voltage up to -40V
 • Low quiescent current at 100µA
 • Pulse frequency modulation maintains high efficiency (max 90%)
 • 100kHz to 320kHz switching frequency
 • Power-Saving shutdown mode (8µA 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