TPS65217: periodically voltage drop on SYS pin

Howard Zou

Part Number: TPS65217
Other Parts Discussed in Thread: AM3354,

Hi,

my customer is using TPS65217C to power AM3354 and has some issue.

They power TPS65217C with regulated 5V applied to AC pin, BAT pin unconnected.

They monitored the 5V input and it's good, no dip. And they can see that the current sourced from 5V is less then 100mA.

But the voltage on SYS pin drop periodically, the waveform is as below, the voltage of SYS will work for 5-6 seconds and then drop for 1 second.

The temperature should not be a problem because no apparent heat up.

Could you please give some suggestions on how to fix the problem? Thanks.

over 6 years ago

0 Brian Berner over 6 years ago

TI__Mastermind 30260 points

This is most likely because the PWR_EN pin is not set high.

When AC power is applied, PWR_EN needs to be set to '1' (high voltage level) or the device will go through a loop like this every 6 seconds (5 second timeout in "Wait PWR_EN" state, then 1s in "Wait 1s" delay timer) as shown in Figure 20 on page 39 of the TPS65217 datasheet.

0 Howard Zou over 6 years ago in reply to Brian Berner

TI__Genius 12365 points

They have pull up PWR_EN externally to 3.3V, but the SYS pin's waveform remains the same

0 Brian Berner over 6 years ago in reply to Howard Zou

TI__Mastermind 30260 points

I need to see a scope shot of PWR_EN pin to confirm the voltage.

All 4 channels of the oscilloscope can be used to help speed up debug process:
1 = SYS
2 = PWR_EN
3 = PB_IN
4 = nRESET

These are the only logic signals that could create behavior similar to the scope shot you provided.

0 Howard Zou over 6 years ago in reply to Brian Berner

TI__Genius 12365 points

Thank you. It's caused by the PB_IN.

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TPS65217: periodically voltage drop on SYS pin