2

L1

OUT

L

P

I

R

1.1

=

´

´

LM5006

www.ti.com

SNVS646B – FEBRUARY 2011 – REVISED MARCH 2013

current switches between these two loops with each transition from on-time to off-time and back to on-time, it is

imperative that the ground end of C1 have a short and direct connection to D1’s anode (or Q1’s source), without

going through vias or a lengthy route. The power dissipation in the LM5006 can be approximated by determining

The power loss in the diode is approximately:

where

•

•

D is the on-time duty cycle

(24)

The average power dissipation in the synchronous rectifier (Q1) is calculated from:

where

•

•

D is the on-time duty cycle

(25)

The power loss in the inductor is approximately:

where

•

•

the 1.1 factor is an approximation for the AC losses

(26)

If it is expected that the internal dissipation of the LM5006 will produce excessive junction temperatures during

normal operation, good use of the PC board’s ground plane can help to dissipate heat. Additionally the use of

wide PC board traces, where possible, can help 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) can help

reduce the junction temperature.

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