MIC47300 Datasheet, PDF (9/11 Pages) Micrel Semiconductor – 3A, Low Voltage, Adjustable LDO Regulator with Dual Input Supply

Micrel, Inc.
Application Information
Adjustable Regulator Design
The MIC47300 allows programming the output down to
0.9V. From the typical application in Figure 1, the output
voltage is set by placing a resistor divider network from
OUT to GND and is determined by the following
equation:
V_OUT
=
0.9 × ⎜⎛ ^R1
⎝ ^R2
+ 1⎟⎞
⎠
where V_OUT is the desired output voltage.
The resistor value between V_OUT and the adjust pin
should not exceed 10kΩ. Larger values can cause
instability. The resistor values are calculated from the
above equation, resulting in the following:
R1
=
R2
×
⎜⎜⎝⎛
V_OUT
0.9
− 1_{⎟⎟⎠⎞}
Evaluation Board Layout
The MIC47300 evaluation board layout is shown in
Figures 2 and 3. For customer application boards,
recommended variations include using a static resistor
for R2 in place of the potentiometer as well as the
elimination of all test points and jumper options that are
included on the MIC47300 evaluation board.
MIC47300
Figure 2. MIC47300 EVB Top Layer
October 2009
Figure 3. MIC47300 EVB Bottom Layer
9
M9999-102309-A