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Battery Management - Chargers Forum
BQ24070 - Startup with battery only fails
I'm successfully using BQ24070 in a project. Everything works as expected, but there is a single effect I can not explain.
The problem is: Starting with no power from AC adapter and the battery is also not connected. If I then connect the
battery first time , I do not get sufficient power at OUT pin. After the battery is disconnected and immediately connected
second time , everything is ok.
I found that if OUT voltage is below 0.2 V, I just get 2.0V (+0.5V saw-tooth ripple) after battery connection. If OUT voltage is
more than 0.2 V (approximately), everything works.
Is there an advice what I'm doing wrong ?
In your case, there are no power sources and the battery is inserted, the output should track the battery voltage if there is no load (<10 mA of load) on the output. If a load is present, that keeps the output more than 200 mV below the battery, a short-circuit condition is declared.
If that is the case, the load has to be removed to recover. A capacitor can be placed on the DPPM pin to delay implementing the short-circuit mode and get unrestricted (not limited) current.
Thank you. It fixes my problem.
I did not expect it , because normally there is always a load at the output. Anyway , it works.
If I would switch to the BQ24079, I assume , such an issues would not appear with that device. Would it be an alternative device to the BQ24070 (in USB mode) with the advantage to disconnect the battery by SYSOFF?
Thank you very much for your help.
Try to add a cap on the DPPM mode to delay the short circuit mode. This may help as well.
Regarding the bq24079, the short circuit protection without source IN still exists . If the OUT voltage falls below the BAT voltage by 250mV for longer than tDGL(SC2), OUT is turned off. Then short circuit recovery timer then starts counting. After tREC(SC2), OUT turns on and attempts to restart. This ON/OFF cycle will continue until the overload condition is removed.
Thanks for the information about BQ24079. I'll keep using BQ24070 (also more easy to get).
Adding a cap fixes my issue perfectly.
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