TPS548D22EVM-784: Intern LDO output problem.

Olin Zhang

Hi team,

When I tested the TPS548D22EVM-784, I found that the voltage overshoot occurred as shown in the BP pin before reaching 2.93V.In general, LDOs do not have this problem. Please explain the reason for this voltage overshoot.

Thank you!

over 7 years ago

0 JohnTucker over 7 years ago

TI__Guru**** 191445 points

Olin,

We'll get someone to look a this after the holiday.

0 Newey Yakamna over 7 years ago in reply to JohnTucker

TI__Intellectual 1520 points

Hi Olin,

I believe this due to your power supply to the VIN. Vin and VDD is connected on the EVM via 1 ohm resistor. Would you please try a different power supply? I've attached a picture of the LDO output with different power supply for your reference.

Thanks,

Amnat

0 Olin Zhang over 7 years ago in reply to Newey Yakamna

TI__Prodigy 630 points

Thank for your reply! I have changed two voltage sources or there is such a voltage overshoot, but at this time I also think it is a problem with the voltage source.

0 Newey Yakamna over 7 years ago in reply to Olin Zhang

TI__Intellectual 1520 points

You're welcome!

0 Olin Zhang over 7 years ago in reply to Newey Yakamna

TI__Prodigy 630 points

Hi Amnat,

In order to observe the influence of the input voltage source on the LDO output, I also detected the input voltage and the BP pin and found that there is no voltage overshoot on the input voltage source. In the figure, channel 1 is the LDO output, the BP pin, and channel 2 is the input voltage.I think the influence of the input voltage source can be eliminated. Do you think there are other factors that influence it? Or is this method wrong?

Thank you.

0 Newey Yakamna over 7 years ago in reply to Olin Zhang

TI__Intellectual 1520 points

HI Olin,
From the earlier picture I've posted on here, one voltage source seems to ramp up much faster than another. Have you tried a different voltage source that can ramp up faster than the one that produce the BP spike? What is your concern about this spike since it's still within the BP threshold?
Thank you.
Amnat

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TPS548D22EVM-784: Intern LDO output problem.