AM335x - RTC signals connexion for RTC subsystem only

Benjamin KOSICKI

Hello,

Currently we are working on an AM335x system based with a TPS65910A3 and a battery, and we wish use the RTC subsystem only (and not the RTC mode only).

The SPRUH73i (p.880) describes that we need connect the input CAP_VDD_RTC to VDD_CORE.

If we lose the main power supply, the TPS65910A3 supplied the RTC power supply through the battery and not the Core voltage, on this case the AM335x RTC lost his power supply and we lost the RTC functionnality.

Did we need connect the RTC power supply to the CAP_VDD_RTC on our use ?

By advance thank you,

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Benjamin,

Is my understanding correct: you need the RTC functional when the processor is powered down? In this case you should use the same connections as the ones used for RTC-only mode.

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

Prodigy 130 points

Hi Biser,

on details, we need to use the RTC when the processor is off but we don't to use the RTC-only mode, the PMIC_POWER_EN and RTC_Wakeup signals are not connected to the PMIC.

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

TI__Guru**** 393215 points

OK, you can leave PMIC_POWER_EN floating and EXT_WAKEUP tied to GND. The other connections should be:

VDDS_RTC - tied to VRTC LDO of PMIC (this will be operational when backup battery is present).

CAP_VDD_RTC - 1 uF decoupling capacitor to GND.

RTC_KALDO_ENn - tied to VDDS_RTC.

RTC_PWRONRSTn - 1.8 V RTC power on reset.

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

Prodigy 130 points

Biser,

Thank you for your support !

Have a good day,

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AM335x - RTC signals connexion for RTC subsystem only