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TPS92512HV: design check

Vincenzo Pizzolante
Mastermind 23271 points
Part Number: TPS92512HV

hi all,

a customer of mine is experiencing high IC temperature w/ TPS92512HV, under these working  conditions:

- VIN = 45...51V

- LED - 43V, 1.05Amp

- FSW = 500KHz

- L = 68uH, ISAT = 2Amp

for what I can see, it seems VIN min too close to VLED so that the (embedded) FET are driven in linear region (not really in class D).

also reducing the ripple (AC losses) might help.

but I would like to hear your recommnadation, assuming the FSW can't be changed...

I tried w/ Webench but seems it can't design w/ this part (can't say why, frankly)

I was considering taking EVM, samples, etc, but would take long time...

If you have a PoC / similar design to speed up the process i would really appreciate it...

thanks a lot in advance

KR

Vincenzo

  • 0
    TI__Mastermind 25500 points

    Hello Vincenzo,

    Over 45W is a lot of power for such a small device, particularly at high duty cycles where most of the power is dissipated in the FET rather than the diode. It may just be that at that high an input voltage and switching frequency the dissipation in the package is just too high. There are power dissipation equations in the datasheet that can be used to estimate it.

    In any case lower ripple would help a little. A lot more copper for heatsinking would help a lot more. If it isn't possible to get the temperature to a reasonable level then the only option is to reduce the switching frequency. AC losses are proportional to the switching frequency so that would make a big difference. Unfortunately AC losses are also proportional to VIN^2, so at high input voltage applications like this it is the only option if heatsinking isn't sufficient.

    For this power level and input voltage another device in a bigger package or a controller would be a better bet if 500kHz is a hard requirement.

    Regards,

    Clint