ZHCSIM4H April 2009 – November 2014 LM25011 , LM25011-Q1
PRODUCTION DATA.
The power dissipation within the LM25011 can be approximated by determining the total conversion loss (PIN – POUT) of the circuit, and then subtracting the power losses in the free-wheeling diode, the sense resistor, and the inductor. The power loss in the diode is approximately:
where IOUT is the load current, VF is the forward voltage drop of the diode, and D is the on-time duty cycle. The power loss in the sense resistor is:
The power loss in the inductor is approximately:
where RL is the dc resistance of the inductor, and the 1.1 factor is an approximation for the ac losses. If it is expected that the internal dissipation of the LM25011 will produce excessive junction temperatures during normal operation, good use of the ground plane of the PC board can help to dissipate heat. Additionally the use of wide PC board traces, where possible, can help conduct heat away from the IC pins. 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.