LM5175: Excessive temperature

Bodo Staeblein

Part Number: LM5175
Other Parts Discussed in Thread: LM5176

We have exactly this behavior that the controller temperature is already above 65 ° C without load. The problem is that of about 200 assemblies that are already manufactured, only about 10% show this behavior. The others are at least 30 ° C cooler.

An idea where to look?

What was the problem solution in the previously curtailed project?

over 6 years ago

0 Youhao Xi over 6 years ago

TI__Guru* 78240 points

Hi Bodo,

65C under no load does not sounds right. Could you share your schematic for an review? What are the VIN and VOUT condition? And the switching frequency? What MODE do you select?

Thanks,
Youhao Xi

0 Bodo Staeblein over 6 years ago in reply to Youhao Xi

Prodigy 70 points

Hi Youhao Xi, thanks for answer.

Vin comes from stabilized power supply 24,0 VDC.

Vout goes to a batterie abt. 22V ... 29V with diode against current flow in the output of the converter.

CCM - mode.

f = 250 kHz.

schematic: 180903_PSUOU

0 Youhao Xi over 6 years ago in reply to Bodo Staeblein

TI__Guru* 78240 points

Hi Bodo,

Can you re-attach the schematic? The link is broken and I cannot see it.

Thanks,
Youhao

0 Bodo Staeblein over 6 years ago in reply to Youhao Xi

Prodigy 70 points

No problem, hope will work now better.

180903_PSUOU_REV6.pdf

0 Bodo Staeblein over 6 years ago in reply to Bodo Staeblein

Prodigy 70 points

Hi Youhao,
works the link? Any idea what we can look for in the IC circuit?

Best Greetings
Bodo

0 Youhao Xi over 6 years ago in reply to Bodo Staeblein

TI__Guru* 78240 points

Hi Bodo,

Can you measure the VCC and also the BOOT1 to SW1, and BOOT2 to SW2 voltages on the board of hot MOSFETs?

Thanks,
Youhao

0 Bodo Staeblein over 6 years ago in reply to Youhao Xi

Prodigy 70 points

Hi Youhao,

we apologize for the late reply. We bypassed the problem by changing the LM5175
to the LM5176. Here we could no longer observe these temperatures.

Thanks again for the effort.

Thanks Bodo.

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LM5175: Excessive temperature