BQ24296M: Charging current limited to 0.6 - 0.7 A

Maciej Maciej

Part Number: BQ24296M

Hi,

I have a problem with BQ24296M. The maximum charging current that it achive is 0.7A even if it is set to be 1.5A (by RILIM).

Could you please check if the problem is with hardware design or I set registers incorrectly?

Here go the scheme of connections:

The registers are set as below:

REG00 = 0x37,
REG01 = 0x1B,
REG02 = 0x60,
REG03 = 0x11,
REG04 = 0xB2,
REG05 = 0x8C,
REG06 = 0x73,
REG07 = 0x00,
REG08 = 0xAC,
REG09 = 0x00.

Regards.

over 8 years ago

0 Joel Hernandez II over 8 years ago

TI__Mastermind 25800 points

Hey Maciej,

It seems that you have a Micro-USB port attached to VBUS, according to your schematic.

Are you applying power from a standard USB port on a laptop/desktop or are you connected to a wall adapter?

Based on the registers, and your RILIM setting it seems that the part is in VINDPM, meaning your input source cannot handle support as much current as is being requested.

Regards,

Joel H

0 Maciej Maciej over 8 years ago in reply to Joel Hernandez II

Prodigy 60 points

Hi Joel,
Thank you for your reply.

I am applying power from wall adapter which for sure can give output current up to 2A. I have checked on three different wall adapters and situation is the same on every one. I also tried to use over a dozen boards to exclude bad soldering but nothing has changed.
I am charging 2600mAh Li-ion so 0.7A charging current is way to low for my project.

Regards,
Maciej

0 Joel Hernandez II over 8 years ago in reply to Maciej Maciej

TI__Mastermind 25800 points

Hey Maciej,

Can you measure the actual resistance on ILIM?

It also looks like you have SYS pulled to a 'VCC' of some sort. How much load current are you pulling from SYS?

Lastly, please measure the voltage on the VBUS pin if you have the ability to do so. Make sure it is above the VINDPM threshold, which is set to 4.36V according to your register settings.

Regards,
Joel H

0 Maciej Maciej over 8 years ago in reply to Joel Hernandez II

Prodigy 60 points

Hi Joel,
The actual resistance on ILIM is 298Ohm.
Current load from SYS is something about 30-50 mA.
VBUS voltage is 4.30V so I have changed VINDPM threshold to 4.20V and finally I reached charging current near 1A (depends on wall adapters). I have also tried to connect not the wall adapter but Lab Power Supply but unfortunately nothing has changed. Is it possible to reach 1.5A charging current?

Regards,
Maciej

0 Joel Hernandez II over 8 years ago in reply to Maciej Maciej

TI__Mastermind 25800 points

Hey Maciej,

I sounds like you have a lot of line impedance going to VBUS. I would ask that you increase the the power supply voltage to ~5.5V, even 6V and see if this persists.

If your line impedance is so much that 1A of current drops the VBUS voltage to the VINDPM threshold, you will likely see this.

Regards,

Joel H

0 Maciej Maciej over 8 years ago in reply to Joel Hernandez II

Prodigy 60 points

Hey Joel,
When I change supply voltage to 5,5V or 6V - nothing is changing and charger is still charging with 1A.
I checked the VBUS voltage and it is above VINDPM threshold also if the battery is charging with wall adapter.

Regards,
Maciej

0 Joel Hernandez II over 8 years ago in reply to Maciej Maciej

TI__Mastermind 25800 points

Hey Maciej,

Another question I forgot to ask is: what is the battery voltage that is applied at the BAT pin (not cell voltage)?

Regards,

Joel H

0 Maciej Maciej over 8 years ago in reply to Joel Hernandez II

Prodigy 60 points

Hey Joel,

The battery voltage on the BAT pin is 4,05V, while on the cell is 3,83V.

Regards,
Maciej

0 Joel Hernandez II over 8 years ago in reply to Maciej Maciej

TI__Mastermind 25800 points

hey Maciej,

The charger may already be in CV mode at that point, and the current will begin to taper down.

Can you try lowering the battery voltage?

Regards,

Joel H

0 Maciej Maciej over 8 years ago in reply to Joel Hernandez II

Prodigy 60 points

Hey Joel,

Thanks for help! When the battery voltage is lower the charger is charging correctly!

Best regards,
Maciej

0 Joel Hernandez II over 8 years ago in reply to Maciej Maciej

TI__Mastermind 25800 points

Hey Maciej,

I'm glad that helped. Just one last comment:

To increase the amount of time the charger is in CC mode, try to improve the line impedance from the battery to the BAT pin. Make this as small as possible.

Regards,

Joel H

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BQ24296M: Charging current limited to 0.6 - 0.7 A