L4973 3.5 A step down switching regulator Features Up to 3.5 A step down converter Operating input voltage from 8 V to 55 V 3.3 V and 5.1 V (1%) fixed output, and DIP-18 (12+3+3) SO-20 (12+4+4) adjustable outputs from: 0.5 V to 50 V (3.3 type) Description 5.1 V to 50 V (5.1 type) Frequency adjustable up to 300 kHz The L4973 is a step down monolithic power switching regulator delivering 3.5 A at fixed Voltage feed forward voltages of 3.3 V or 5.1 V and using a simple Zero load current operation (min. 1 mA) external divider output adjustable voltage up to Internal current limiting (pulse by pulse and 50V. Realized in BCD mixed technology, the HICCUP mode) device uses an internal power D-MOS transistor (with a typical R of 0.15 ) to obtain very DS(on) Precise 5.1 V (1.5%) reference voltage high efficiency and very fast switching times. externally available Switching frequency up to 300 kHz are achievable Input/output synchronization function (the maximum power dissipation of the packages Inhibit for zero current consumption (100 mA must be observed). typ. at V = 24 V) A wide input voltage range between 8 V to 55 V CC and output voltages regulated from 3.3 V to 40 V Protection against feedback disconnection cover the majority of the today applications. Thermal shutdown Features of this new generation of DC-DC Output over voltage protection converter includes pulse by pulse current limit, hiccup mode for output short circuit protection, Soft-start function voltage feed forward regulation, soft-start, input/output synchronization, protection against feedback loop disconnection, inhibit for zero current consumption and thermal shutdown. Packages available are in plastic dual in line, DIP- 18 (12+3+3) for standard assembly, and SO20 (12+4+4) for SMD assembly. Figure 1. Internal schematic diagram V (8V to 55V) CC C 7 8 12 BOOT R 9 OSC V (3.3V or 5.1V) L4973 O 1 3 C C2 L1 IN 4,5,6,10 2 13,14,15 16 17 11 R COMP C C D1 C OSC SS OUT C COMP D97IN554A February 2009 Rev 18 1/28 www.st.com 28Contents L4973 Contents 1 Block diagram 3 2 Pin settings 3 2.1 Pin connection 3 2.2 Pin description 4 3 Electrical data 5 3.1 Maximum ratings 5 3.2 Thermal data . 5 4 Electrical characteristics . 6 5 Evaluation board 9 6 Application circuit 12 7 Typical characteristics 13 8 Application ideas . 21 9 Package mechanical data 23 10 Order code 26 11 Revision history . 27 2/28