AN-1578| Application Note
LM25575 Evaluation Board
LM25575 Evaluation Board
National Semiconductor Application Note 1578 Robert Bell January 2007
Introduction
The LM25575 evaluation board is designed to provide the design engineer with a fully functional power converter based on Emulated Current Mode Control to evaluate the LM25575 regulator IC. The evaluation board provides a 5V output with a 1.5A current capability. The ultra-wide input voltage ranges from 7V to 42V. The design operates at 300kHz, a good compromise between conversion efficiency and solution size. The printed circuit board consists of 2 layers of 2 ounce copper 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 LM25575 datasheet for complete circuit design information. The performance of the evaluation board is as follows: Input Range: 7 to 42V Output Voltage: 5V Output Current: 0 to 1.5A Frequency of Operation: 300 KHz Board Size: 2.6 X 1 X 0.4 inches Load Regulation: 1% Line Regulation: 0.1% Over Current Limiting
Evaluation Board Schematic
30007001
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 1.8A. Turn off the power supply. Connect the power supply to the Vin terminals. Step 2: Connect the load, with a 1.5A capability, to the Vout terminals. Positive connection to J2 and negative connection to J3.
2007 National Semiconductor Corporation 300070
Step 3: The SD pin should be left open for normal operation. Step 4: Set Vin to 24V 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 1.5 Amps. Step 6: Slowly sweep the input voltage from 7 to 42V, Vout should remain in regulation with a nominal 5V output. Step 7: Temporally short the SD 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 2.1A. The power supply (Vin source) current limit may
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AN-1578
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