TPS65400: Problems occur at low temperatures

Charles Jeon

Expert 2975 points

Part Number: TPS65400
Other Parts Discussed in Thread: LMK04808

Hi team

My client configured the system with the following blocks.

The circuit value of the TPS65400 are shown below.

LMK04808 does not work properly when testing -5 ° operation to chamber.

Normally, PLL2 should operate in cascade after PLL1 of LMK04808 operates.

The problem is that PLL1 operates normally at low temperature, but PLL2 does not work.

Please check that the above circuit constants are properly designed.

0 Sam(MPAA) Zhang over 6 years ago

Hi Charles,

May I ask where is the PLL 1/2? Do you mean the waveform at switching node is not good?

Regards,
Sam

0 Charles Jeon over 6 years ago in reply to Sam(MPAA) Zhang

Expert 2975 points

Hi sam

When the power is turned off and on again at a low temperature, I have found a problem that the SW4 output is 2.6V to 2.8V.

I have found that the SS / PG Pin is connected to the VDDD of the TPS65400 in the customer circuit as shown below.

The customer wants to use the SS / PG pin as a soft start function.

Is there a voltage drop problem when VDDD and SS / PG are directly connected as shown below?

And please check if there is a problem with the compensation circuit value.

0 Sam(MPAA) Zhang over 6 years ago in reply to Charles Jeon

Hi,

Let's close this thread and discuss this issue in the other thread you opened. Thanks!

Regards,
Sam

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