Battery detection with the TPS65721

Christopher Payne

Other Parts Discussed in Thread: TPS65721

I am trying to find a reliable way to tell if a battery is detached using the TPS65721 while plugged in over USB. Right now I am using the comparator to see if the battery voltage is less than 2.2V (register 0x05). Is there a more definitive way to tell if a battery is detached? I also tried the CH_FAULT bit in register 0x06 but it did not change when a battery was removed.

over 9 years ago

0 Kevin LaRosa over 9 years ago

TI__Genius 17380 points

Hi Christopher,

Using register 0x05 is a good approach. Only thing I would add is to use the VBAT_COMP interrupt if you are not already, described in section 8.3.10.3. VBAT_COMP should have a rising edge when VBAT drops below VBAT[1:0] which can trigger the interrupt.

0 Christopher Payne over 9 years ago in reply to Kevin LaRosa

Intellectual 665 points

Great, thank you Kevin.

0 Christopher Payne over 9 years ago in reply to Kevin LaRosa

Intellectual 665 points

I do have another issue that I'm not sure about. When I have a battery attached, the bit VBAT_COMP returns 0 continually to show the voltage is above the threshold as expected. However, when the battery is not attached, it keeps going back and forth between 1 and 0. For example, it will maybe return 1 for 5 seconds to show that it is below the threshold which is expected with the battery being detached, but then it will return 0 for the next 5 seconds and continue the cycle indefinitely. Do you have any ideas on what might cause this?

0 Kevin LaRosa over 9 years ago in reply to Christopher Payne

TI__Genius 17380 points

Hi Christopher,

When no battery is detected, the device checks for battery by inserting current into the VBAT net and discharging it while checking voltage with VBAT_COMP. This is outlined in section 8.3.3.3 Battery Detection and Recharge.

0 Christopher Payne over 9 years ago in reply to Kevin LaRosa

Intellectual 665 points

Somehow I skipped over this section, thank you Kevin.

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Battery detection with the TPS65721