TPS65910: VBACKUP Consumption when device is OFF State

Leandro Teixeira

Part Number: TPS65910
Other Parts Discussed in Thread: AM3351

I am using the PMIC TPS65910A31A1 with sitara AM3351. I am using the RTC from the PMIC with the internal oscillator and the VBACKUP supply is the battery CR2032(3V).

My case is:

When the device is ON, the current in the VBACKUP pin is 0 A. (correct)

When i put PWRON in '0' for 8 seconds the PMIC goes to OFF State. In this state (OFF) the current in VBACKUP pin is 0,35mA, and in the datasheet the number for this situation is max. 42uA. (Wrong).

The RTC keep the clock, but with this current, the CR2032(168mAh).is valid for only 20 days . When the correct will be at least 160 days.

So, what is wrong with my circuit?

Thanks.

over 6 years ago

0 Krishnamurthy Hegde over 6 years ago

TI__Expert 8730 points

Hi,

I have assigned your request to responsible Applications Engineer and we will get back to you as soon as possible.

Regards,

Murthy

0 Kevin LaRosa over 6 years ago

TI__Genius 17380 points

Hi Leandro,

Are you connecting the VRTC output to anything? If you are connecting it to the processor, then the extra load could be coming from the processor.

One additional note: the TPS65910A31A1 has the VRTC forced into full-power mode in the OFF state so I would expect about 20 uA of extra current based on the VRTC LDO ground current spec (section 5.13). If you used the TPS65910A3A1 then the VRTC LDO should only consume 3 uA instead of 23 uA.

0 Leandro Teixeira over 6 years ago in reply to Kevin LaRosa

Intellectual 300 points

we are connecting the VRTC in the PU/PD resistors (10k) boot mode, VDDS_RTC (backup) of the AM3351 and two PU resistors (EXT_WAKEUP and VRTC_DETECT) of the AM3351.

0 Leandro Teixeira over 6 years ago in reply to Leandro Teixeira

Intellectual 300 points

How can we put the VRTC supply to low power mode on device OFF STATE?
We wrote in the register 0x1E of the PMIC the value 0x01 and it is not solved.

When we turn off the device the supply VRTC still consuming 350uA.

0 Kevin LaRosa over 6 years ago in reply to Leandro Teixeira

TI__Genius 17380 points

Hi Leandro,

Are the pull-ups all measuring 1.8V? If any of the pull-ups are being forced low, then that could explain your issue. 1.8V / 10kohm = 180 uA.

It looks like processor should only be using ~20 uA based on this link: processors.wiki.ti.com/.../AM335x_Power_Consumption_Summary

If you have the ability to disconnect various loads from the VRTC, you could try to figure out where the current is going with a digital multimeter.

Power management

Power management forum

TPS65910: VBACKUP Consumption when device is OFF State