bq32000: Issue with battery draining

user5087263

Part Number: BQ32000
Other Parts Discussed in Thread: BQ32002

When processor is not connected and when the board is not powered on we get 0.2mA current due to battery. A 0.1uF capacitor is connected to Vback pin with battery voltage net.

Can we know what is the issue?

Regards,

Bhavishya AJ

over 7 years ago

0 Alan O over 7 years ago

TI__Mastermind 32575 points

This is a known behavior of the device documented in the datasheet section below. This device is best suited for wall-powered systems with backup battery, and not purely battery-powered systems.

8.2.2.3 Utilizing the Backup Supply
In order for the bq32000 to achieve a low backup supply current as specified in the Electrical Characteristics, the VCC pin must be initialized after every total power loss situation. Initialization Is achieved by powering on VCC with a voltage between 3 to 3.6 V for at least 1 ms immediately after the backup supply is connected. If the VCC is not
powered on while connecting the backup supply, then the expected leakage current from VBACK will be much greater than specified.

Regards,
Alan

0 user5087263 over 7 years ago in reply to Alan O

Intellectual 390 points

Hi,

Thanks for the information.

We are using external power supply where Vcc is 3.3V. Its is clearly mentioned in data sheet of bq32000, maximum Iback is 1.5uA. But When we measured it is 230uA.

When we rested following "8.2.2.3 Utilizing the Backup Supply", there was no major considerable difference.

Is this a known issue?

As the device does not meet the datasheet detail, is there an errata for this?

Regards,

Bhavishya AJ

0 Alan O over 7 years ago in reply to user5087263

TI__Mastermind 32575 points

Please note the Iback test condition and footnote in the datasheet. Maybe this condition is different from your condition and explains the difference in your test result?

Also, please see this forum post for more background on this issue:
e2e.ti.com/.../295753

Alan

0 Alan O over 7 years ago in reply to user5087263

TI__Mastermind 32575 points

Also, did you try removing the 0.1uF capacitor, in case it is causing leakage on Vback?

0 user5087263 over 7 years ago in reply to Alan O

Intellectual 390 points

Hi,
We tried it. before it was 0.22mA and after removing 0.1uF it is 0.15mA. there is no much considerable changes.

Regards,
Bhavishya AJ

0 Alan O over 7 years ago in reply to user5087263

TI__Mastermind 32575 points

Is this Iback current reproducible on multiple boards? Can you remove the battery and replace it after VCC is powered on, and re-test Iback?

0 Alan O over 7 years ago in reply to user5087263

TI__Mastermind 32575 points

Please share your schematic too.

Alan

0 user5087263 over 7 years ago in reply to Alan O

Intellectual 390 points

Hi,

I have answered in red for your queries.

Is this Iback current reproducible on multiple boards?

We have checked in multiple boards. Same issue is found.

Can you remove the battery and replace it after VCC is powered on, and re-test Iback?

We have tested the way you suggested but no considerable changes.

Regards,

Bhavishya AJ

0 user5087263 over 7 years ago in reply to Alan O

Intellectual 390 points

It is same as in datasheet

0 Alan O over 7 years ago in reply to user5087263

TI__Mastermind 32575 points

What is the battery voltage with model part# you are using?
Is the trickle charger path is disabled when Iback is measured (after Vcc has been pulsed as required per datasheet section 8.2.2.3)?
If you replace with BQ32002 (pin compatible), do you still measure higher than expected Iback?
By the way, what is your end-equipment for this RTC application, and is your battery soldered or in a holder?

Thanks,
Alan

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bq32000: Issue with battery draining