TPS65910A3 wrong VRTC

Ashika Ashok11

We have interfaced TPS65910A3A1RSL with AM3352BZCZ60 processor.

We are connecting the VRTC LDO output to the VDDS_RTC(D7) pin of the processorAM3352BZCZ60.

When we are not powering on the PMIC we are noticing VDDS_RTC voltage going to 1.8V. But when we are powering on the PMIC we are noticing a voltage rise of 2.4V at the VDDS_RTC pin of the processor.

The other outputs of the PMIC are working fine.

Another point to be noted is
If we disconnect VRTC(of PMIC) then VRTC of PMIC comes back to 1.8V but VDDS_RTC of processor stays at2.4V.
How can VDDS_RTC source 2.4V when it is a power input pin?

Kindly help us on this issue.

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi,

You have a schematic or layout error in your board, that's causing leakage to the RTC power domain. Check carefully all your processor power rails. Especially check the RTC connections. Use this table for guidelines: processors.wiki.ti.com/.../AM335x_Schematic_Checklist

0 peaves over 9 years ago in reply to Biser Gatchev-XID

TI__Guru 62945 points

Do you have a crystal circuit or an LVCMOS clock source connected to the OSC1 terminals (RTC_XTALIN and RTC_XTALOUT)? If you are sourcing a clock into RTC_XTALIN, what is the voltage of the signal?

Are you sourcing signals to any of the other RTC inputs (EXT_WAKEUP, RTC_KALDO_ENn, RTC_PWRONRSTn)? If so, what is the voltage of these signals?

All of these inputs are limited to 1.8 volts LVCMOS.

Regards,
Paul

0 Ashika Ashok11 over 9 years ago in reply to peaves

Intellectual 380 points

We are using crystal at RTC_XTALIN and RTC_XTALOUT. The voltage seen at RTC_XTALIN is around 2.52V

We are grounding RTC_KALDO_ENn pin through 10k.

EXT_WAKEUP of processor is connected to INT1 pin of PMIC. We have also connected that pin to ground via 10k.

RTC_PWRONRSTn is connected to VRTC of PMIC via 15k resistor. we have also connected a cap of 100nF to RTC_PWRONRSTn and GND.

Regards

Ashika Ashok

0 Biser Gatchev-XID over 9 years ago in reply to Ashika Ashok11

TI__Guru**** 393215 points

Please disconnect EXT_WAKEUP of processor from INT1 pin of PMIC and check if the issue still exists. This connection is wrong anyway.

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TPS65910A3 wrong VRTC