LM3557

LM3557 Step-Up Converter for White LED Applications November 2004 LM3557 Step-Up Converter for White LED Applications General Description The LM3557 is a complete solution for white LED drive applications. With minimal external component 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 component implementations. The LM3557 switches at a fixed-frequency of 1.25 MHz, which allows for the use of small external components. Also, the LM3557 has a wide input voltage range to take advantage of multi-cell input applications. With small external components, 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 Compensation 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 Components Typical Application Circuit 20131601 FIGURE 1. Backlight Configuration © 2004 National Semiconductor Corporation DS201316 www.national.com LM3557 Connection Diagram Top View 20131602 8-Lead Thin Leadless Leadframe Package See NS Pack...