[AM3354BZCE] Custom board does not boot from RTC-only mode

Martino Facchin

Hello,

I'm working on a custom board with early samples of AM3354BZCE (Silicon Rev 2.1)
The wiring between TPS62217A and the processor are derived from the schematics of BeagleBone White.

The problem is related with the RTC-only (quasi-off) mode, with TPS in sleep and only the 1.8V_LDO1 power rail active.
From this configuration, using the push button, I should be able to wake up the board as described in the TPS manual, page 17.

But the processor does not respond to nWAKEUP interrupt pulling up PWR_EN as it should, so the TPS shuts down itself after 5 seconds.
Obviously we lose the rtc date, which is critical for the application.

Is there a way to solve the problem? The new silicon revision shouldn't have corrected the rtc bug?
If it is needed to solve the problem, we are using version 0x181 of M3 companion processor from Arago sources.

Thank you so much
Regards,

Martino

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Martino,

What is exactly the part number of your PMIC? There is no TPS62217A part manufactured by TI.

0 Biser Gatchev-XID over 12 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

OK, I guess it must be TPS65217A. Do you have an external pullup resistor to VRTC on the WAKEUP line? This is an open-drain PMIC output.

0 Martino Facchin over 12 years ago in reply to Biser Gatchev-XID

Prodigy 130 points

Thank you for the quick reply. Yes there is a 75kohm pullup on that line.

Of course the PMIC is TPS65217A, sorry for the typo.

Regards,

Martino

0 Biser Gatchev-XID over 12 years ago in reply to Martino Facchin

TI__Guru**** 393215 points

Very strange. Have you checked the WAKEUP signal with a scope? Maybe 75kOhm is too much, there is a 4.7kOhm on the Beaglebone. Do you have a 32.768kHz crystal on the processor?

0 Martino Facchin over 12 years ago in reply to Biser Gatchev-XID

Prodigy 130 points

Yes there is the 32k crystal and it's clocking during rtc-only mode.

I'll try to change the pullup and report the results.

Best regards,

Martino

0 Martino Facchin over 12 years ago in reply to Martino Facchin

Prodigy 130 points

We managed to solve the problem. In fact it was software based.

For anyone interested, the register that handles wake from RTC only mode is RTC_PMIC, which default state for field EXT_WAKEUP_EN is 0.

Regards

Martino

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[AM3354BZCE] Custom board does not boot from RTC-only mode