• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 430 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

BQ24070: charging deeply discharged battery

BQ24070EVM: Charging Deeply Discharged Battery

Eric Smith77
Intellectual 370 points
Part Number: BQ24070EVM
Other Parts Discussed in Thread: BQ24070

I have been having issues with the BQ24070EVM providing no output voltage in two scenarios explained below. In both scenarios, the input voltage is set to 5.25V/2A, the charge enable pin is high, the Mode pin is high, the ISET2 pin is set to 0.5 (high), the TS resistance (TP2) is set to 52.5kΩ, and the DPPM resistance (TP1) is set to 33.8kΩ.

  1. The first scenario starts with a dead battery (e.g., battery voltage at 0V) connected to the BAT pin and a 16Ω load plugged in on the output. The charge input of 5.25V is applied and the output voltage floats around 0.25V or less. After waiting for about 30 minutes, the output voltage remains low. No current is being drawn on the charge input.
  2. The second scenario starts with disconnecting the battery completely with a 16Ω load plugged in on the output. The charge input of 5.25V is applied and the output voltage exhibits the same behavior as explained in the first scenario. No current is being drawn on the charge input.

The datasheet for the BQ24070 states that it should be able to work just fine in both of the scenarios above. It seems like the BQ24070EVM is entering short circuit mode and never gets out of it.

Both of these scenarios can be resolved if I remove the load. If I remove the load, the output drives to 4.4V in both scenarios and the battery begins to charge at the precharge current for the first scenario. I can then connect the load after that, and things work as desired. I currently have no way of externally removing the load from the output on my design. Is there any way that I can resolve this without disconnecting the load from the output? If it is a short circuit issue, can I disable or delay the short circuit functionality on the chip?

I have seen a couple of other support questions on the forum related to this problem, but there was no resolution in either of them.

This charger is exactly what I need for my design. I need a charger that can charge the battery up to 1.5A as well as supplying up to a 500mA load at the same time. I also need the charger to have dynamic power path management so that if the customer plugs in an input that cannot supply 1.5A charge to the batteries, it will still work. The DPPM on the BQ24070 works exactly as I need in my testing I have done. If the BQ24070 cannot work in the two scenarios I listed above, I will need to find another option for my charger/system supply. Is there another charger that would be able to work for me if this one cannot work?

  • +1
    TI__Mastermind 23410 points

    Hi Eric,

    Yes, this would look to be the short circuit detection occurring on startup. Based on what you've said it does look like a short circuit that disabled the input FET. What you can do is try and temporarily pull the OUT voltage using a switch from the input as described in 8.3.5 Short-Circuit Recovery. This is simply to exit the short circuit that is occurring when you turn on the device. You may need to try a few different pullup resistors to the input to ensure the output is above the short circuit threshold (1V is good).

    The goal is to pull the output voltage high enough that the input FET to be enabled again. Once the output gets pulled up, the device should begin to output 4.4V which then you can switch off the pull up. 

    Best Regards,

    Anthony Pham