TPS755: High current applications

Cherry Zhou

Part Number: TPS755
Other Parts Discussed in Thread: TPS7A53,

Hi team,

The customer would like to use TPS75533KTT for high current applications:

The output is 3.3V at an input voltage of 5V, with a voltage drop of 1.7V. Based on the maximum current of 5A in the manual, the heat power of the chip is 8.5W, which translates to a temperature rise of 328℃ (the parameter on the manual is that the bottom is not copper-coated), which has already exceeded the operating temperature of the chip. In this case, how to get the chip current to 5A? Is it all about cooling?

Could you help check this case? Thanks.

Best Regards,

Cherry

over 2 years ago

+1 Stephen Ziel over 2 years ago

TI__Mastermind 37065 points

Hi Cherry,

You are correct in that this application will need significant cooling to achieve this load current. Even a thermally saturated PCB design will be unlikely to keep this device cool enough, as thermally saturated PCB's can usually only provide 50% of the thermal resistance you see in the datasheet. Thus, 38.7 C/W becomes approximately 20 C/W in the best case scenario, and this is still not enough to keep the device cool. The customer would then need some form of active cooling which is usually costly to build into the system.

The customer can either use a switching regulator which may need an external EMI filter, or they can parallel LDO's which will not need an EMI filter design. We have new collateral which makes designing in parallel LDOs easy to do. The customer would need 3 LDOs to dissipate the heat. Instead of 3 parallel TPS755 LDO's, I would recommend 3x TPS7A53. The TPS7A53 is a newer device with much better performance than the TPS755. The $1k price for the TPS755 is $2.9, while the $1k price for the TPS7A53 is $1.19. Please see my links below for details on parallel LDOs. I filled out an example in the calculator which is where I would probably start for this application.