L4978 Datasheet | STMicroelectronics

DESCRIPTION The L4978 is a step down monolithic power switching regulator delivering 2A at a voltage between 3.3V and 50V (selected by a simple external divider). Realized in BCD mixed technology, the device uses an internal power D-MOS transistor (with a typical Rdson of 0.25Ω) to obtain very high efficency and high switching speed. TYPICAL APPLICATION CIRCUIT Vi=8V to 55V 5 R1 20K 3 C1 220µF 63V C7 220n F C2 2.7n F 2 7 Minidip SO16W ORDERING NUMBERS: L4978 (Minidip) L4978D (SO16) A switching frequency up to 500KHz is achievable (the maximum power dissipation of the packages must be observed). A wide input voltage range between 8V to 55V and output voltages regulated from 3.3V to 50V cover the majority of today’s applications. Features of this new generations of DC-DC converter include pulse-by-pulse current limit, hiccup mode for short circuit protection, voltage feedforward regulation, soft-start, protection against feedback loop disconnection, inhibit for zero current consumption and thermal shutdown. The device is available in plastic dual in line, MINIDIP 8 for standard assembly, and SO16W for SMD assembly. 4 1 6 L1 126µH (77120) D1 GI SB560 C8 330µF VO=3.3V/2A C5 100n F R2 9.1K C4 22n F C6 100n F D98IN837A May 2000 1/12 BLOCK DIAGRAM VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE SS_INH 2 INHIBIT SOFTSTART 3.3V P FB 7 8 E/A INTERNAL REFERENCE INTERNAL SUPPLY 5.1V 6 PWM BOOT 3.3V Q DRIVE OSCILLATOR 1 GND CBOOT CHARGE AT LIGHT LOADS 3 OSC 4 OUT D97IN594 PIN CONNECTIONS N.C. GND 1 2 3 4 5 6 7 8 D97IN596 16 15 14 13 12 11 10 9 N.C. N.C. FB P BOOT VCC N.C. N.C. GND SS_INH OSC OUT 1 2 3 4 D97IN595 8 7 6 5 FB P BOOT VCC SS_INH OSC OUT OUT N.C. N.C. Minidip SO16W PIN...