MIC5159 Datasheet, PDF (9/23 Pages) Micrel Semiconductor – PROGRAMMABLE CURRENT LIMIT UCAP LDO REGULATOR CONTROLLER

MIC5159
Layout Considerations
Input and output capacitor placement should be as close as
possible to the input and output, respectively. Trace resis-
tance between the current sense and the MOSFET source
should be minimized. Trace resistance will increase dropout
voltage. This is more of a factor at higher output currents.
Also, a minimum amount of distance between the gate pin, on
the MIC5159, and the P-Channel MOSFET gate is recom-
mended. A long trace can create a small parasitic inductor.
This, coupled to the gate capacitance of the MOSFET, can
create a high frequency tank circuit. A small 50Ω resistor in
series with the gate may be required to eliminate high-
frequency noise.
Micrel
Adjustable Regulator Design
The MIC5159 allows programming the output voltage any-
where between 1.235V to V_IN. Two resistors are used. See
Figure 4. The resistor values are calculated by:
R1=
R2
×
 _{}
V_OUT
1.235

−
1^{}
Where V_OUT is the desired output voltage.
V_IN
R_S
Si3445
V_OUT
MIC5159-x.x
IS
GATE
IN
ADJ
EN _GND
R1 ^CceOr^Ua^Tm=ic10µF
R2
Figure 4. Adjustable Regulator Design
April 2004
9
M9999-041204