SC1628

HIGH-EFFICIENCY STEP-UP DC-DC CONVERTER January 30, 1998 SC1628 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DESCRIPTION The SC1628 is a high performance step-up DC-DC converter, designed to drive an external power switch to generate programmable positive voltages. In the particularly suitable LCD contrast bias and flash memory programming power supply applications, typical full load efficiencies are 85% to 95%. The 4V to 24V input operation range allows the SC1628 to be powered directly by the battery pack in most batterypowered applications for greater efficiency. The output voltage can be scaled to 40V or greater 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 down to 8µA in shutdown mode. With a switching frequency range of 90kHz to 250kHz, 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 Low quiescent current at 100µA Pulse-skipping and pulse-frequency modulation maintain high efficiency (max. 95%) 90kHz to 250kHz oscillator frequency Power-saving shutdown mode (8µA typical) Push-pull driver output BLOCK DIAGRAM APPLICATIONS Flash memory programming power supply Positive LCD contrast bias for notebook and palm top computers ...