BQ25306: BQ25306 cann't charge

Hi,

   What is the status of the STAT pin? Is it indicating charge in progress, off, or toggling at 1Hz frequency?

What is the range of battery voltage that you see charging occur like normal?

Hi Kedar，

I describe our situation in detail,

1. We charge at 12V, and the battery is fully charged at 8.4V;

2. When the battery is discharged below 6.0V, it will enter over-discharge protection, the voltage output is 0V ;

3. Then plugged in the charger, BQ25306 will not charge, and there will not start 35mA trickle charge;

4. At this time, the status of STAT is low, the waveform of SW is as shown in the figure below,it's DC 1.0V, and the voltage of REGN is 4.96V

Hi Kedar，

If the battery voltage is between 6.5V-8.2V, BQ25306 will charge normally

Hi,

Through further testing, I found that only when the battery voltage is less than VBat_Short, the BQ25306 will not charge in this case, and there is no 35mA charging current. Other Pre-charge and Fast Charge are normal.

Please help，thanks！

Hi,

  VBAT_SHORT = 2V for falling threshold. This feature has been thoroughly verified. Do you have an external gauge or protector in your system? If that external part has an undervoltage lockout voltage through which the path disconnects, then there could be an issue. have you tested your configuration on the evaluation board?

Hi，

We did not add external gauge or protector

1. We actually use a 1.27V battery to charge, the charging current is aways 0mA, STAT is low, and after 2 hours, STAT starts toggling at 1Hz frequency 

2. We switch to using a 2.5V battery to charge, the charging is normal, and the charging current is 75mA;

Disconnect the PMID power supply to the downstream system. At this time, when the battery voltage is 1.27V, there will be a charging current of 30mA.

But our design must be compatible with the adapter to start the machine directly, is there any solution?

Hi,

   If the system load is too much for the adapter to provide with the short current of 30mA will not be enough. This is intended as using your system load when battery is discharged so low is dangerous. If system load is active, and adapter is removed, then battery will supply the system load. When battery is discharged so low, providing discharge current to supply external system load on pmid is dangerous. Shouldn't system architecture be such that battery cannot be discharged so low? It would be better to include a protector with an undervoltage lockout

Hi,

   Let me test this configuration in lab on the EVM. What is the load current from PMID in your application?

Hi，

I have tested this，when the PMID current exceeds 30mA, BQ25306 will not charge, it should be current limited by the first MOSFET at the VBUS input. Our system load is about 500mA. 

Hi，

Our current design is same as Typical Application of  section 10.2.2，Please refer to the schamatic attachment befor.

The Typical Application will not hlep for this issue.

Our current design is the same as the typical application, please refer to the previous schematic attachment. If the power supply of system is not through PMID, but directly through VBUS, is this feasible?

For typical applications, just the PMID is disconnected, and then directly connected to VBUS, and the others remain unchanged.