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User's Guide
SNVA330B–January 2009–Revised April 2013
AN-1801 LP38511TJ-ADJ Evaluation Board
1 Introduction
This board is designed to allow the evaluation of the LP38511TJ-ADJ voltage regulator. Each board is
assembled and tested in the factory. This evaluation board has the TO-263 THIN 5-lead package
mounted, and the output voltage is set to 1.20 V.
2 General Description
The LP38511TJ-ADJ is an adjustable LDO linear regulator capable of suppling up to 800mA of output
current, and incorporates an Enable.
The device has been designed to work with 10 µF input and output ceramic capacitors. Footprints areas
for C
IN
and C
OUT
will allow for a variety of sizes.
3 Operation
The input voltage, applied between V
IN
and GND, must be no less than 2.25 V, which is the low end of the
operating range voltage, no greater than 5.5 V, which is the high end of the operating rating voltage.
The input voltage should also be at least 500 mV greater than the set V
OUT
.
Loads can be connected to V
OUT
with reference to GND.
V
OUT
and V
IN
test points are provided on the board to allow accurate measurements directly onto the input
and output pins of the device, eliminating any voltage drop on the PCB traces or connecting wires to the
load.
4 Setting V
OUT
The output voltage is set using the external resistive divider R1 and R2. The output voltage is given by the
formula:
V
OUT
= V
ADJ
x (1 + (R1 / R2)) (1)
It is recommended that the values selected for R1 and R2 are such that the parallel value is less than 1.00
kΩ. This is to prevent internal parasitic capacitances on the ADJ pin from interfering with the F
Z
pole set
by R1 and C
FF
.
( (R1 x R2) / (R1 + R2) ) ≤ 1.00 kΩ (2)
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1
SNVA330B–January 2009–Revised April 2013 AN-1801 LP38511TJ-ADJ Evaluation Board
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