BQ24075: BQ24075 not charging

Lukas Bereuter

Part Number: BQ24075

Dear community

I have designed a Li-Ion charger with the BQ24075 based on the schematic below.

Problem: When I connect a voltage at IN (5V, current limit >2A), the LED at the CHG pin is illuminated, but the battery is not charged (I measured the battery current)

Further information:

- Without anything applied at the IN pin, the battery voltage appears at the OUT pin, so this seems to work as expected

- I connected a 10k NTC at the TS pin

- The only difference I can see compared to the reference schematic is that EN2 and the charge LED are connected to IN instead of OUT. As those are digital terminals, I don't expect problems from this

Any idea what could be the problem?

Best regards,

Lukas

over 4 years ago

0 Raheem over 4 years ago

TI__Mastermind 21590 points

Can you measure the voltage on TS? is CE low? Is there any load on VOUT?

0 Lukas Bereuter over 4 years ago in reply to Raheem

Prodigy 90 points

Thanks for your reply!

- Voltage on the TS pin is 0V (a 10k NTC is connected)

- CE is low (connected to GND)

- Load on VOUT: Same behaviour with load (20mA) and without load.

0 Raheem over 4 years ago in reply to Lukas Bereuter

TI__Mastermind 21590 points

Voltage on TS pin should be between 300mV and 2.1V. Can you try replacing the IC.

Is the 10k resistor properly connected to the NTC pin

0 Lukas Bereuter over 4 years ago in reply to Raheem

Prodigy 90 points

- I replaced the IC several times, still no voltage at the TS pin. It is the same problem on all of the 4 PCBs. But: the LED at the CHG pin is illuminated. How can that be when it's not charging?

- Also the 10k resistor is properly connected to the TS pin

0 Raheem over 4 years ago in reply to Lukas Bereuter

TI__Mastermind 21590 points

Can you do a continuity test on TS pin to make sure it is not shorted to ground when the resistor isn't present?

The device will never charge with the TS pin at 0V

0 Lukas Bereuter over 4 years ago in reply to Raheem

Prodigy 90 points

I measured the current coming out of the TS pin: there is no current flow out of the TS pin.

I also measured the resistance between TS and GND. It is 10k when the NTC is placed and high impedance without NTC present.

Could this be a batch issue? As I said, it's the same problems on all 4 PCBs...

0 Raheem over 4 years ago in reply to Lukas Bereuter

TI__Mastermind 21590 points

Hello,

I'll be surprised its a batch issue but you can try different units. Can you double check that VIN is present when you checked the TS pin?

0 Raheem over 4 years ago in reply to Raheem

TI__Mastermind 21590 points

Hello,

Any updates here?

0 Lukas Bereuter over 4 years ago in reply to Raheem

Prodigy 90 points

I am unavailable this week and will try to check it next week. Thanks.

0 Lukas Bereuter over 4 years ago in reply to Raheem

Prodigy 90 points

Yes, VIN is present. Here's the voltage levels on all the pins with VIN connected to 5V:

PIN1,4,6,8,12,15) 0V

PIN2,3) 3.6V (battery voltage)

PIN5,10,11,13) 5V

PIN14) 2.2V

PIN9) drives low -> LED is illuminated. But the battery is not charged (current consumption is only 5mA, which comes from the LED)

When there is no voltage connected to VIN, the following voltages appear:

PIN2,3,10,11) 3.6V (battery voltage)

all the other PINs: 0V

0 Raheem over 4 years ago in reply to Lukas Bereuter

TI__Mastermind 21590 points

Hello,

Pin 12 should be round 2.25V and pin 1 should be between 0.3V and 2.1V. I think the unit you have might be damaged. Can you try doing a unit swap.

0 Lukas Bereuter over 4 years ago in reply to Raheem

Prodigy 90 points

I did try a unit swap, it did not help. Also, I have the same issue on 4 identical PCBs. So I think it's not a problem of a single damaged unit.

0 Raheem over 4 years ago in reply to Lukas Bereuter

TI__Mastermind 21590 points

Hello Lukas,

I doubt that this is a batch issue but you can try another batch of ICs.

Also did you try just checking the board without the IC present to make sure all the pins are connected properly on the board?

Power management

Power management forum

BQ24075: BQ24075 not charging