AN-1596| Application Note

LM5116 Evaluation Board

National Semiconductor Application Note 1596 Robert Sheehan May 2007

Introduction
The LM5116 evaluation board is designed to provide the design engineer with a fully functional power converter based on Emulated Current Mode Control to evaluate the LM5116 controller IC. The evaluation board provides a 5V output with a 7A current capability. The wide input voltage ranges from 7V to 60V. The design operates at 250kHz, a good compromise between conversion efficiency and solution size. The printed circuit board consists of 4 layers, 2 ounce copper top and bottom, 1 ounce copper internal layers on FR4 material with a thickness of 0.06 inches. This application note contains the evaluation board schematic, Bill-of-Materials (BOM) and a quick setup procedure. Refer to the LM5116 datasheet for complete circuit design information.

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FIGURE 2. Efficiency with 5.6 uH Pulse Inductor

Powering and Loading Considerations
Read this entire page prior to attempting to power the evaluation board. QUICK SETUP PROCEDURE Step 1: Set the power supply current limit to 15A. Turn off the power supply. Connect the power supply to the VIN terminals. Step 2: Connect the load, with a 7A capability, to the VOUT terminals. Positive connection to P3 and negative connection to P4. Step 3: The EN pin should be left open for normal operation. Step 4: Set VIN to 48V with no load applied. VOUT should be in regulation with a nominal 5V output. Step 5: Slowly increase the load while monitoring the output voltage, VOUT should remain in regulation with a nominal 5V output as the load is increased up to 7 Amps. Step 6: Slowly sweep the input voltage from 7 to 60V, VOUT should remain in regulation with a nominal 5V output. Step 7: Temporally short the EN pin to GND to check the shutdown function. Step 8: Increase the load beyond the normal range to check current limiting. The output current should limit at approximately 11A. Cooling is critical during t
his step.

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FIGURE 1. Efficiency with 6 uH Cooper Inductor The performance of the evaluation board is as follows: Input Range: 7V to 60V Output Voltage: 5V Output Current: 0 to 7A Frequency of Operation: 250 kHz Board Size: 2.55 X 2.65 X 0.5 inches Load Regulation: 1% Line Regulation: 0.1% Over Current Limiting

AN-1596

2007 National Semiconductor Corporation

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