AM335x + TPS65910 start-up problem

Prad1

Other Parts Discussed in Thread: TPS65910, AM3352

Hi,

I am sorry for posting TPS65910 question here, I will ask the same in the PMU forum
but I would like to know if there are any suggestions in this forum also.

Our customer board has TPS65910AA1 as PMIC IC to power up AM3352.
But unfortunately the TPS65910AA1 is not working (so AM3352 is not working).
There is no output from the TPS65910 IC even after applying power.
Seems like either the IC is dead or the circuit is wrong.

All the connections are done as per the TI's reference boards Schematics.
PWRHOLD and PWRON pins are connected as below.

PWRHOLD -> Connected to an external 3.3V power to keep it High
PWRON -> As we don't need the push button, PWRON pin is left floating

And below are the results of few test points after applying power to TPS65910.

INT1 -> 0V
SLEEP -> 0V
PWRON -> 5V
BOOT0 -> 0V
BOOT1 -> 1V
PWRHOLD -> 3.3V

Just in case I am attaching the our schematics.

Please let me know what else should be tested to analyse the problem
and is it ok to leave PWRON pin floating if the push button is not necessary?

Regards
Prad

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

Hi Prad,

You have a 10kOhm serial resistor, R109 on PWRHOLD. The PWRHOLD pin has an internal pulldown enabled by default. Suggest you change the 10kOhm to 0Ohm.

Also it seems that the I2C1 interface is used. Software expects the PMIC to be connected to I2C0. R138 and R139 should also be mounted.

0 Prad1 over 10 years ago in reply to Biser Gatchev-XID

Genius 3825 points

Hi Biser,

Thank you so much.
We will make the change according to your suggestions.

Regarding I2C0, we are not using the I2C1 to read the internal register etc.So it is left unconnected.
Just for the confirmation, should I2C0 be connected even if don't communicate between the ICs?

Regards
Prad

0 Biser Gatchev-XID over 10 years ago in reply to Prad1

TI__Guru**** 393215 points

If you don't expect to change the processor OPP (by default the PMIC will start with OPP100 voltages), then no.

0 Biser Gatchev-XID over 10 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Correction on my first reply - disregard it.

Just noticed that you have been following the Starter Kit schematic. This expects a PWRON button action. If you want to start directly when input voltage is applied you should tie PWRHOLD to the input voltage instead of VAUX33. Just bear in mind that PWRHOLD input must not exceed +5.5V, so if your input voltage is higher a resistive divider should be placed.

0 Prad1 over 10 years ago in reply to Biser Gatchev-XID

Genius 3825 points

Hi Biser,

Thank you for the correction.

Actually the circuit was designed to connect PWRHOLD to VAUX33,
but as it doesn't work properly we tried to connect it to some external 3.3V supply
and got 5V output at PWRON and 0V at SLEEP pin

Please let me ask one more question,
since we don't use any battery backup or RTC functions and there is no VBAT.
So the VBACKUP,VCC1,VCC2 etc all are connected to 5V supply.
Is it ok to connect VBACKUP to 5V directly?

Regards.
Prad.

0 Biser Gatchev-XID over 10 years ago in reply to Prad1

TI__Guru**** 393215 points

Yes, this is the correct connection if backup is not used.

0 Miteshkumar Dalabhai Patel over 8 years ago in reply to Biser Gatchev-XID

TI__Intellectual 1900 points

Hi Prad,

One of my customer was facing similar issue of startup. They have made 25 boards & out of 25, 18 boards were working & rest of the 7 boards were not working.

After lots of debugging I found that if we change capacitor value on VRTC pin to 0.1uF all the boards were working perfectly fine.

My observations was when we put 2.2uF, VRTC pin was showing less than 1V & DC to DC converters were not getting enough supply for enable threshold.

I hope this will helps.

regards,
Mitesh

0 Kummi over 8 years ago in reply to Miteshkumar Dalabhai Patel

Mastermind 6220 points

Hi Mitesh,

Thank you so much for the information.

Even our customer is having the same problem with the VRTC Capacitor.
Did you find out the reason behind this issue?

I have posted the question on TPS forum but didn't get the answer yet.
e2e.ti.com/.../501127

Best Regards
Kummi

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AM335x + TPS65910 start-up problem