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# BQ24650: Charging Problem

Part Number: BQ24650

Hi,

We have made the 3-cell Li-ion 2A Battery Charger using the BQ24650. But the charging is not happening, If i remove the battery pack, the STAT1 LED start glowing and STAT2 LED OFF If I connect the battery, the STAT1 & STAT2 LED are OFF, no charging is happening.

VREF: 3.298V

REGN: 5.974V

MPPSET: 0.868V

VFB: 5.586V

TS: 1.979V

VBAT: 10.06V

HDRV: 10.06V

LODRV:0V

SRN: 10.06V

Attached the schematic. Please suggest a solution to solve the charging problem....

Regards,

Nishanth M

BQ24650RVAR_Charger.pdf

• Hello,

What happens if you increase your input voltage to 20 V? Your input voltage may not have enough headroom for your output voltage of 12.6 V because of layout and setup.

Thanks,

Mike Emanuel

• Hi,

If I increase the input voltage to above the 19V, the STAT1 and STAT2 LED are OFF, but charging is not happening. That time its taking less than 1mA current at input power side.

1. If the battery is disconnected and input voltage is below 19V means, it takes 16mA current at input side and STAT1 LED is ON.

2. If the battery is connected and input voltage is 14 ~ 22V, it takes less than 1mA current at input side and STAT1 & STAT2 LED are OFF.

Thanks and Regards,

Nishanth M

• Dear Nishanth,

You need to adjust your MPPSET voltage divider if you want it to work with 14 V input (0.868 MPPSET is too low). From your schematic I calculated 0.942 V on the pin, but your measurement says 0.868 V. What is your MPPSET when you apply other input voltages?

The datasheet says, "If the MPPSET pin voltage is forced below 1.2 V, the BQ24650 stays in the input voltage regulation loop while the output current is zero." Please adjust the voltage divider appropriately.

Thanks,

Mike Emanuel

• Hi,

Thanks for the reply... I assembled one more PCB. Now I changed the MPPSET value to 14V (499K & 47K). In second PCB the charging is happening and all the protections also working well. But the problem is chip is heating once the charging starts. I don't know why the BQ chip is heating when charging starts. All other components are in normal temperature. All the Pin voltages are correct level only. Please help me to solve the heat issues...

• Hello,

If the part is working in the desired manner but is getting too hot, the layout probably needs to be adjusted. Please follow the layout guidelines in the datasheet, making sure all vias and traces are properly sized for the current they are using. In addition, please make sure the thermal pad is connected to ground with enough thermal vias.

Thanks,

Mike Emanuel