MIC25400 Datasheet, PDF (21/27 Pages) Micrel Semiconductor – 2A Dual Output PWM Synchronous Buck Regulator IC

Micrel, Inc.
RC Snubber
• Place the RC snubber on the same side of the board
and as close as possible to the low-side MOSFET.
Low-side MOSFET
• Low-side drive MOSFET traces (LSD pin-to-
MOSFET gate pin) must be short and routed over a
ground plane. The ground plane should be the
connection between the MOSFET source and
PGND.
• Chose a low-side MOSFET with a high CGS/CGD
ratio and a low internal gate resistance to minimize
the effect of dv/dt inducted turn-on.
• Do not put a resistor between the LSD output and
MIC25400
the gate.
• Use a 4.5V Vgs rated MOSFET. Its higher gate
threshold voltage is more immune to glitches than a
2.5V or 3.3V rated MOSFET. MOSFETs that are
rated for operation at less than 4.5V_GS should not be
used.
High-side MOSFET
• Add a 20 ohm resistor in series with the boost pin.
This will slow down the turn-on time of the high-side
MOSFET while leaving the turn-off time unaffected.
January 2011
21
M9999-020111-C