AM57x short on 3 power supply rails

Mani Kumar

Intellectual 320 points

Other Parts Discussed in Thread: TPS659039-Q1, TPS659037, TPS65916, X5777BXGABC, X5777AXGABC

Hi,

I have used TPS659039 PMIC and AM57XX processor for one of our project.

At present facing low impedance issue (0.5 ohm) for three voltage rails.

I have provided below snapshot for usage of PMIC in this application.

Faced same issue earlier, but rectified the problem by un-mounting PMIC and processor. Then assembled new PMIC and processor.

Again facing similar issue where suspecting problem at PMIC and processor by usage of toneohm meter.

Common observations during this failure at both these instances are as follows:

Unit in which this card is assembled has the feature to use two batteries which are controlled by usage of DPDT switch
When the unit is powered-on (with usage of battery) power good LEDs on the board are not turned-on. After further debugging identified short at three voltage rails

SMPS7 --> VCC_Core --> used between PMIC and processor
SMPS9 --> VCC_1V8 --> used between PMIC and processor
VCC_3V3 --> Connected to processor only. GPIOs of PMIC will control the voltage of this section

Not able to identify the root cause for this. Please check and let us know your observations on this.

Regards,

Mani

over 9 years ago

0 Eric Hackett over 9 years ago

TI__Guru 74282 points

Mani,

The appropriate applications engineer has been notified of your post and will respond accordingly.

Regards,

0 Karl Wallinger over 9 years ago

TI__Genius 16410 points

Hello Mani,

First, please confirm the orderable part number you are using. From your block diagram, it looks like O9039A344IZWSRQ1. Is that correct? Please refer to the TPS659039-Q1 User's Guide to make sure you're using the right device configuration for your system.

Second, can you tell if the PMIC or processor is shorted? If you remove the output inductor from SMPS7 and SMPS9, you should be able to measure the impedance on each side, to see if the short is through the PMIC or through the processor.

If the short is through the PMIC SMPS, it may indicate some overvoltage or undervoltage spike on the SMPS. You can refer to the layout section of the datasheet for a description of taking spike measurements to make sure the device is operating within its absolute maximum rating.

If it's on the processor side, it may indicate that too high of a voltage is being provided to the processor. If this is the case, please double check the OTP configuration for your system in the user's guide, to make sure the processor domains are being supplied by the correct PMIC supplies.

Regards,
Karl

0 Mani Kumar over 9 years ago in reply to Karl Wallinger

Intellectual 320 points

Hello Karl,

Thanks for your reply,

PMIC part number used is TPS659039CIZWSRQ1.

Not able to identify whether short is happened at PMIC or Processor even after isolating output inductors from SMPS7 and SMPS9. Because inductor output voltage is directly connected to SMPS7_FDBK and SMPS9_FDBK pins of PMIC.

First time when i have faced the problem identified that short is at processor pins only (After un-mounting verified on BGA balls)

Kindly note the following:

We are using same design for more than a year
Issue of voltage short happened second time on same card, the common observation is that while changing supply connections from external power supply to battery. this issue is observed
We are not able to co-relate whether there is issue while changing power supply switching? Please let us know your thoughts on this.

Regards,

Mani

0 Karl Wallinger over 9 years ago in reply to Mani Kumar

TI__Genius 16410 points

Mani,

Can you please send me a message using the e-mail in my profile? I'd like to discuss this offline with you.

Regards,
Karl

0 Karl Wallinger over 8 years ago in reply to Karl Wallinger

TI__Genius 16410 points

Hi Mani,

Thanks for the offline discussion. Since this is a short on the processor, I expect it is an overvoltage (ESD or otherwise) on the processor supply pins. I suggest starting with these debugging techniques:

1. Check the nominal output voltage during operation to make sure they are within processor limits (confirm correct by you)

2. Check if software is setting the PMIC outputs higher than the boot voltage using I2C to set the SMPSx_VOLTAGE register for the appropriate domains.

3. Check the power sequence meets the processor requirements.

4. Measure the processor supply voltage at the VDD, VDDSHVn, and VDDS18V decoupling capacitors during operation to measure transients. Expected transients should be 1%-5%. Excessive PCB trace resistance from PMIC to processor could cause higher ripple.

I'm going to move this to the Sitara forum as well, in case they have other recommendations to debug the processor short.

Regards,
Karl

0 Biser Gatchev-XID over 8 years ago in reply to Karl Wallinger

TI__Guru**** 393215 points

Why is TPS659039CIZWSRQ1 used for AM57x?

According to section 8.1 from the AM571x Datasheet SR2.0 Rev. B:
"TPS65916 or TPS659037 are the Power Management ICs (PMICs) that should be used for the Device designs. TI requires use of these PMICs... etc."

According to section 8.1 from the AM572x Datasheet SR2.0 Rev. B:
"TPS659037 is the Power Management IC (PMIC) that should be used for the Device designs. TI requires use of this PMIC... etc."

0 Mani Kumar over 8 years ago in reply to Biser Gatchev-XID

Intellectual 320 points

Hello Biser,

Thanks for your reply.

We have referred to TI-VAYU EVM schematic, in this for TPS659039 used for X5777BXGABC.

Reference Link: www.ti.com/.../sprr210.pdf

Please check and suggest.

Regards,
Mani

0 Biser Gatchev-XID over 8 years ago in reply to Mani Kumar

TI__Guru**** 393215 points

Which processor exactly are you using?

0 Mani Kumar over 8 years ago in reply to Biser Gatchev-XID

Intellectual 320 points

Hello Biser,

Thanks for your reply.

Processor that we have used is X5777AXGABC. For this part also reference design used has TPS659039 as PMIC.

Regards,
Mani

0 Biser Gatchev-XID over 8 years ago in reply to Mani Kumar

TI__Guru**** 393215 points

Sorry, Vayu devices are not supported on this forum. This device should be supported on the DRAx Infotainment SoCs Forum: e2e.ti.com/.../1020 Please ask there.

0 Mani Kumar over 8 years ago in reply to Biser Gatchev-XID

Intellectual 320 points

Hello Biser,

I have referred Vayu and made custom design. The issue that I have referred to is about our custom design only

Regards,
Mani

0 Biser Gatchev-XID over 8 years ago in reply to Mani Kumar

TI__Guru**** 393215 points

Please read my previous post.

0 Rogerio Almeida over 8 years ago in reply to Mani Kumar

TI__Mastermind 26215 points

Mani,
This is a bit confusing....is the problem that you are facing on AM57x family or Automotive Processors part numbers?

0 Mani Kumar over 8 years ago in reply to Rogerio Almeida

Intellectual 320 points

Hello Rogerio,

Problem that we are facing is from AM57x family of sitara processor.

Regards,
Mani

0 Rogerio Almeida over 8 years ago in reply to Mani Kumar

TI__Mastermind 26215 points

Mani,
Thanks...now Biser can help you....(I am glad you clarified....AM57x and some automotive ICs share the same platform, but there are features that are not enabled in our AM57x but are in Auto Parts and vice-versa....)

0 Biser Gatchev-XID over 8 years ago in reply to Rogerio Almeida

TI__Guru**** 393215 points

This totally contradicts what was posted by Mani in this same thread on Jan. 01, 2017:
e2e.ti.com/.../2068239

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AM57x short on 3 power supply rails