TPS40428EVM-594: Overshoot on startup

Michael Balourdas

Part Number: TPS40428EVM-594

Hello,

My customer is experiencing overshoot at startup on the Eval module The output doesn't seem to be following VREF during startup. TON_RISE for VREF is 2.7msec, but the device is starting in less than 1msec with almost 100mV overshoot. After startup, performance appears to function as desired. Is this a known issue? Is there a setting that needs to be changed?

Thanks,

Michael

over 6 years ago

0 Qian Chen over 6 years ago

TI__Mastermind 24075 points

Hi Michael,

Do you have startup waveform customer is seeing?
The typical startup waveform is available on EVM user guide.

Thanks
Qian

0 Michael Balourdas over 6 years ago in reply to Qian Chen

TI__Expert 5455 points

Hi Qian,

Here's the waveform:

0 Qian Chen over 6 years ago in reply to Michael Balourdas

TI__Mastermind 24075 points

Hi Michael,

Did customer do any change on EVM?
What is blue curve in the waveform.
VREF is an internal voltage, how did customer measure VREF?

Thanks
Qian

0 Michael Balourdas over 6 years ago in reply to Qian Chen

TI__Expert 5455 points

Hi Qian,

They changed the parameters to Vout=0.9V, dual phase single output, with fsw=250kHz.

L1/L2>0.32uH
COUT>1600uF (16x100uFx6.3V 1210)
R24>80.6k
R13>20k
C16>2.2nF
R12>698
C17>1.5n
C26>68n
R16>1.21k

They measured Vref across the bottom feedback resistor.

Thanks,
Michael

0 Qian Chen over 6 years ago in reply to Michael Balourdas

TI__Mastermind 24075 points

This problem is supported offline.
I will close this post.

Thanks
Qian

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TPS40428EVM-594: Overshoot on startup