PTH12050W: PTH12050WAD running hotter than expected

Al Paulhus

Part Number: PTH12050W
Other Parts Discussed in Thread: LMZ31506, LMZ31707

We use these Texas Instruments DC-DC converters in multiple designs. The PTH12050W is used to convert 12V down to both 3.3V and 1.2V.

Issue we are seeing is that the modules that convert down to 3.3V run very hot to the touch. Touching the magnetics can burn, while the other 1.2V does not.

The 3.3V converter is very lightly loaded, less than 100mA maximum compared with the 1.2V which uses 2A. The datasheet does not specify a minimum load requirement. The converters work fine, why the drastic difference in their temperature? Heat is not good for magnetics.

over 3 years ago

0 Yitzhak Bolurian over 3 years ago

TI__Mastermind 18370 points

Hi Al,

I guess the 1.2V one is of PTH12050L type and the 3.3V one is of PTH12050W type.

Sorry for the trouble caused. Do you see this issue with many units or just one?

What is the input current when the module is enabled and when it is disabled?

Regards,

Yitzhak Bolurian

0 Al Paulhus over 3 years ago in reply to Yitzhak Bolurian

Prodigy 170 points

Yitzhak,

Both 1.2V and 3.3V sources use thw PTH12050W part. We use 2K resistor to set 3.3V while the 1.2V is left "open" or unconnected. We are seeing this on many of the converters. Current draw on the 12V input side of the 3.3V module is 175mA when enabled. When the inhibit pin (4) is brought low, the input current drops to 1mA

0 Yitzhak Bolurian over 3 years ago in reply to Al Paulhus

TI__Mastermind 18370 points

Hi Al,

Thanks for the details. We have started to investigate the reported issue.
We will get back to you as soon as we have any findings.

Regards,

Yitzhak

0 Yitzhak Bolurian over 3 years ago in reply to Al Paulhus

TI__Mastermind 18370 points

Hi Al,

We have investigated this issue further.

The PTH12050W uses an older powdered iron core inductor.

The core loss causes the device to heat up even at no load / light load.

There is a 44°C rise in the inductor at no load.

When Vout is set to 3.3V, the current ripple is higher causing more heat compared to the Vout=1.2 V case.

Newer modules such as LMZ31707 and LMZ31506 will stay much cooler, specially at lighter loads.

Best regards,

Yitzhak

0 Vincent Zhang(BSR) over 3 years ago in reply to Yitzhak Bolurian

TI__Expert 4795 points

Hi,

My colleague will feedback to you early next week.

0 Al Paulhus over 3 years ago in reply to Yitzhak Bolurian

Prodigy 170 points

This device is used in a released product so switching to a different device may not be practical unless its pin compatible. Next question: will this excessive heat possible cause long term damage or early life failure ?

+1 Yitzhak Bolurian over 3 years ago in reply to Al Paulhus

TI__Mastermind 18370 points

Hi Al,

Please look at the SOA graphs on page 6 of the datasheet (Figure 4).
If used according to the safe operating area, there should not be any issues.

Regards,

Yitzhak

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PTH12050W: PTH12050WAD running hotter than expected