LM3557 Datasheet | National Semiconductor

Description The LM3557 is a plete solution for white LED drive applications. With minimal external ponent count, no DC current leakage paths to ground, cycle-by-cycle current limit protection, and output over-voltage protection circuitry, the LM3557 offer superior performance and cost savings over standard DC/DC boost ponent implementations. The LM3557 switches at a fixed-frequency of 1.25 MHz, which allows for the use of small external ponents. Also, the LM3557 has a wide input voltage range to take advantage of multi-cell input applications. With small external ponents, high fixed frequency operation, and wide input voltage range, the LM3557 is the most optimal choice for LED lighting applications. 1.25 MHz Constant-Switching Frequency Output Over-Voltage Protection Input Under-Voltage Protection Cycle-By-Cycle Current Limit TRUE SHUTDOWN: No DC current paths to ground during shutdown n Low Profile Package: < 1 mm Height -8 Pin LLP n No External pensation n n n n n Applications n White LED Display Lighting n Cellular Phones n PDAs Features n VIN Range: 2.7V- 7.5V n Small External ponents Typical Application Circuit FIGURE 1. Backlight Configuration © 2004 National Semiconductor Corporation DS201316 .national. Connection Diagram Top View 8-Lead Thin Leadless Leadframe Package See NS Package Number SDA08A Ordering Information Order Number LM3557SD-2 LM3557SDX-2 Package Marking L147B L147B Supplied As 1k Units, Tape and Reel 4.5k Units, Tape and Reel Pin Description Pin # 1 2 3 4 5 6 7 8 DAP Name Sw1 VIN NC En Ovp Fb Sw2 Gnd DAP Input Voltage Connection No Connection Device Enable Connection Over-Voltage Protection Input Connection Feedback Voltage Connection Drain Connection of an Internal Field Effect Transistor (FET) Switch (Figure 2: N2) Ground Connection Die Attach Pad (DAP), must be soldered to the printed circuit board’s ground plane for enhanced thermal dissipation Description Drain Connection of the Internal Power Field...