MIC38150_10 Datasheet, PDF (10/15 Pages) Micrel Semiconductor – HELDO® 1.5A High Efficiency Low Dropout Regulator

Micrel, Inc.
PCB Layout Guideline
Warning!!! To minimize EMI and output noise, follow
these layout recommendations.
PCB Layout is critical to achieve reliable, stable and
efficient performance. A ground plane is required to
control EMI and minimize the inductance in power,
signal and return paths.
The following guidelines should be followed to insure
proper operation of the MIC38150.
IC
• Place the IC close to the point of load (POL).
• Use fat traces to route the input and output power
lines.
• The exposed pad (ePAD) on the bottom of the IC
must be connected to the PGND pins of the IC.
• Use several vias to connect the ePAD to the ground
plane.
• Signal and power grounds should be kept separate
and connected at only one location.
• Keep the switch node (SW) away from the feedback
(FB) pin.
Input Capacitor
• Place the input capacitor next.
• Place the input capacitors on the same side of the
board and as close to the MIC38150 as possible.
• Keep both the PVIN and PGND connections short.
• Place several vias to the ground plane close to the
input capacitor ground terminal, but not between the
MIC38150
input capacitors and IC pins.
• Use either X7R or X5R dielectric input capacitors.
Do not use Y5V or Z5U type capacitors.
• Do not replace the ceramic input capacitor with any
other type of capacitor. Any type of capacitor can be
placed in parallel with the input capacitor.
• If a Tantalum input capacitor is placed in parallel
with the input capacitor, it must be recommended for
switching regulator applications and the operating
voltage must be derated by 50%.
• In “Hot-Plug” applications, a Tantalum or Electrolytic
bypass capacitor must be used to limit the over-
voltage spike seen on the input supply with power is
suddenly applied.
• The 1µF capacitor, which connects to the AVIN
terminal, must be located right at the IC. The AVIN
terminal is very noise sensitive and placement of the
capacitor is very critical. Connections must be made
with wide trace.
Output Capacitor
• Use a wide trace to connect the VSW output
capacitor ground terminal to the PVIN input
capacitor ground terminal.
• The feedback trace should be separate from the
power trace and connected as close as possible to
the output capacitor.
June 2010
10
M9999-061010-C