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L4978 Datasheet(PDF) 1 Page - STMicroelectronics |
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L4978 Datasheet(HTML) 1 Page - STMicroelectronics |
1 / 13 page 1/13 L4978 May 2005 1 Features ■ 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 300KHz ■ 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 2 DESCRIPTION The L4978 is a step down monolithic power switching regulator delivering 2A at a voltage be- tween 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 300KHz is achievable (the maximum power dissipation of the packages must be observed). A wide input voltage range be- tween 8V to 55V and output voltages regulated from 3.3V to 50V cover the majority of today’s ap- plications. 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, DIP- 8 for standard assembly, and SO16W for SMD as- sembly. 2A STEP DOWN SWITCHING REGULATOR Figure 2. Typical Application Circuit D98IN837A 5 2 8 4 1 L4978 C1 220 µF 63V C8 330 µF VO=3.3V/2A Vi=8V to 55V R1 20K C2 2.7nF R2 9.1K C4 22nF 3 7 L1 126 µH (77120) 6 D1 ST PS3L60U C5 100nF C7 220nF C6 100nF Rev. 9 Figure 1. Packages Table 1. Order Codes Part Number Package L4978 DIP-8 L4978D SO16 L4978D013TR SO16 in Tape & Reel DIP-8 SO16W |
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