Datasheet

LM5117, LM5117-Q1
SNVS698E –APRIL 2011–REVISED MARCH 2013 www.ti.com
Connect all of the low power ground connections (R
UV1
, R
T
, R
FB1
, C
SS
, C
RES
, C
CM
, C
VIN
, C
RAMP
) directly to the
regulator AGND pin. Connect C
VCC
directly to the regulator PGND pin. Note that C
VIN
and C
VCC
must be as
physically close as possible to the IC. AGND and PGND must be directly connected together through a top-side
copper pattern connected to the exposed pad. Ensure no high current flows beneath the underside exposed pad.
The LM5117 has an exposed thermal pad to aid power dissipation. Adding several vias under the exposed pad
helps conduct heat away from the IC. The junction to ambient thermal resistance varies with application. The
most significant variables are the area of copper in the PC board, the number of vias under the exposed pad and
the amount of forced air cooling. The integrity of the solder connection from the IC exposed pad to the PC board
is critical. Excessive voids greatly decrease the thermal dissipation capacity.
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