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L4978

STMicroelectronics
Part Number L4978
Manufacturer STMicroelectronics
Description 2A STEP DOWN SWITCHING REGULATOR
Published Mar 22, 2005
Detailed Description ® L4978 2A STEP DOWN SWITCHING REGULATOR UP TO 2A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 8V TO 55V PRECISE 3...
Datasheet PDF File L4978 PDF File

L4978
L4978

Overview
® L4978 2A STEP DOWN SWITCHING REGULATOR UP TO 2A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 8V TO 55V PRECISE 3.
3V (±1%) INTERNAL 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) INHIBIT FOR ZERO CURRENT CONSUMPTION PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN SOFT START FUNCTION 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 220nF C2 2.
7nF 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.
8 L4978 4 1 6 L1 126µH (77120) D1 GI SB560 C8 330µF VO=3.
3V/2A C5 100nF R2 9.
1K C4 22nF C6 100nF D98IN837A May 2000 1/12 L4978 BLOCK DIAGRAM VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE SS_INH 2 INHIBIT SOFTSTART 3.
3V COMP FB 7 8 E/A INTERNAL REFERENCE INTERNAL SUPPLY 5.
1V 6 PWM BOOT R S 3.
3V Q DRIVE OSCILLATOR 1 GND CBOOT CHARGE AT LIGHT LOADS 3 OSC 4 OUT D97IN594 PIN CO...


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