Datasheet

LM25085, LM25085-Q1
www.ti.com SNVS593H –OCTOBER 2008–REVISED MARCH 2013
The voltage regulation, over-voltage, and current limit comparators are very fast and can respond to short
duration noise pulses. Layout considerations are therefore critical for optimum performance. The layout must be
as neat and compact as possible with all the components as close as possible to their associated pins. Two
major current loops conduct currents which switch very fast, requiring the loops to be as small as possible to
minimize conducted and radiated EMI. The first loop is that formed by C
IN
, Q1, L1, C
OUT
, and back to C
IN
. The
second loop is that formed by D1, L1, C
OUT
, and back to D1. The connection from the anode of D1 to the ground
end of C
IN
must be short and direct. C
IN
must be as close as possible to the VIN and GND pins, and C
VCC
must
be as close as possible to the VIN and VCC pins.
If the anticipated internal power dissipation of the LM25085 will produce excessive junction temperatures during
normal operation, a package option with an exposed pad must be used (HVSSOP-PowerPAD-8 or WSON-8).
Effective use of the PC board ground plane can help dissipate heat. Additionally, the use of wide PC board
traces, where possible, helps conduct heat away from the IC. Judicious positioning of the PC board within the
end product, along with the use of any available air flow (forced or natural convection) also helps reduce the
junction temperature.
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