L4976 Datasheet | STMicroelectronics

® 1A STEP DOWN SWITCHING REGULATOR UP TO 1A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 8V TO 55V PRECISE 5.1V REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM 3.3V TO 50V SWITCHING FREQUENCY ADJUSTABLE UP TO 500KHz VOLTAGE FEEDFORWARD ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING (PULSE-BYPULSE AND HICCUP MODE) PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN DESCRIPTION The L4976 is a step down monolithic power switching regulator delivering 1A 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. A switching frequency up to 250KHz is achievable (the maximum power dissipation of the pack TYPICAL APPLICATION CIRCUIT Minidip SO16W ORDERING NUMBERS: L4976 (Minidip) L4976D (SO16) ages must be observed). A wide input voltage range between 8V to 55V and output voltages regulated from 3.3V to 40V 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, protection against feedback loop disconnection and thermal shutdown. The device is available in plastic dual in line, MINIDIP 8 for standard assembly, and SO16W for SMD assembly. Vi=8V to 55V 5 R1 20K 3 C1 220µF 63V C7 220n F C2 2.7n F 2 7 8 4 1 6 L1 260µH (77120) D1 GI SB360 C8 330µF VO=3.3V/1A R2 9.1K C4 22n F C6 100n F May 2000 1/11 BLOCK DIAGRAM VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE VREF 2 VREF 5.1V P FB 7 8 E/A 3.3V PWM R S Q DRIVE OSCILLATOR CBOOT CHARGE AT LIGHT LOADS INTERNAL REFERENCE 6 BOOT 3.3V 3 OSC 1 GND 4 OUT PIN CONNECTIONS N.C. GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 N.C. N.C. FB P BOOT VCC N.C. N.C. GND VREF OSC OUT 1 2 3 4 8 7 6 5 FB P BOOT VCC VREF OSC OUT OUT N.C....