AN-1479| Application Note
LP38856S-1.2 Evaluation Board
LP38856S-1.2 Evaluation Board
Introduction
This board is designed to allow the evaluation of the LP38856S-1.2 Voltage Regulator. Each board is assembled and tested in the factory. This evaluation board has the TO-263 5-lead package mounted.
National Semiconductor Application Note 1479 Don Jones November 2006
In applications were the LP38856 is operated continuously the Enable pin can be connected directly to VBIAS, or left open. The Enable pin has a 200 k internal resistor to VBIAS. If the Enable pin is left open, care should be taken to minimize any capacitance on the Enable pin, as any capacitance will introduce an RC delay time on the Enable function.
General Description
The LP38856 is a dual-rail LDO linear regulator capable of suppling up to 3A of output current, and incorporates an Enable function The device has been designed to work with 10 uF input and output ceramic capacitors, and 1uF bias capacitors. Footprints areas for CIN and COUT will allow for a variety of sizes.
Operation
The input voltage, applied between VIN and GND, should be at least 1.0V greater than VOUT, and no higher than the applied VBIAS voltage. The bias voltage, applied between VBIAS and GND should be above the minimum bias voltage of 3.0V, and no higher than the maximum of 5.5V. Loads can be connected to VOUT with reference to GND. VOUT and VIN test points are provided on the board to allow accurate measurements directly on the evaluation board, eliminating any voltage drop on the PCB traces or connecting wires to the load. ON/OFF control is provided by supplying a logic level signal to the Enable pin. A minimum VEN value of 1.3V is required at this pin to enable the LDO output. The LDO output will be shutdown when the VEN value is 1.0V or less. The VEN threshold incorporates approximately 100mV of hysteresis.
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FIGURE 1. Enable Thresholds
Hardware
The schematic and layout of the evaluation board are given below:
Schematic Diagram
20193501
Evaluation Board Schematic.
AN-1479
2006 National Semiconductor Corporation
AN201935
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