Maximum current on bq24192

Hi Phien,

1600mA number shouldn't matter on controlling charge current. something else (eg, fault, clamp, protection, etc) may have kicked in, or mistakenly set.

Can you clarify how did you get 2048mA by "following user manual", and how did you "measure" the current to be 400-600mA? What's your input voltage and current at Vbus, and what's your BAT voltage and current, and do you have load at SYS?

Can you also read Reg8 and Reg9? before and after you set to 1600mA+

Do you have a second board to confirm your result?

Best Regards,

Linhong Qin

Hi Linhong Qin,

The default charge current i got in section 9.3.3.1, and i measured charge current by VOM - battery in series (Fluke 87)

My input voltage a Vbus is 12VDC. When it charged at 600mA, The value in Reg7, Reg8, Reg9 is OK.

+ Fast charging,

+Power Good,

+Thermal status: Normal,

+ Bat fault: Normal.

+ Not DPM

+ Input limit current i set : 2A, thermal regulation: 120 (I2C commands)

I think everything was good. I send you my schematic.

I already compared this between 2 board, one can charge up to 2000mA, one is only 1600mA. With board "2000mA" if i set fast charge current > 2000mA, it charged at 400-600mA as board "1600mA". if I set < 2000mA, board "2000mA" charged at this value.

Thanks for your help.

Best Regards,

Phien Nguyen

Hi Phien,

Do you use a real battery? Do you have protections on battery? What's the voltage at BAT pin? It seems something have kicked in at increased charging current. It could be too high battery voltage, or some protection on battery.

By the way, we recommend a 1uF cap at Vbus.

Best Regards,

Linhong

Hi  Linhong Qin,

I tested this board with iPhone and iPad battery, the voltage at BAT pin is in [3600mV, 4300mV] it depended on the voltage of battery.

I use three parallel capacitors (220uF//22uF//1uF) at Vbus.

Below is protected circuit:

The Mosfet Q7 will close before we want to charge.

Thanks and Best regards,

Phien Nguyen

Hi Phien,

Battery voltage plays a big role on charge current(please refer to Datasheet on different charge modes with respect to different battery voltage). You might have gotten away from constant current mode. What's your charge voltage limit? Are you able to measure battery voltage when you see 1.6A or 400mA charge current? Or can you try on a 3.6V battery?

Regards,

Linhong

Hi Linhong Qin,

My charge voltage limit is 4.3V, I send you a example i got: iPad battery voltage (not charge): 3700mV, charge at 1.6A measured voltage is about 3900mV, charge at 400mA (if i set fast charge value more than 1600mA) measured voltage is about 3800mV. So, i think it was still in CC mode.

In your opinion, what's the problem? Configuration code, or hardware design.

Thank you very much.

Best Regards,

Phien Nguyen

Hi Phien,

3.7V BAT voltage is fine. But you also have some other circuit connected to the battery. Is it possible to disconnect them from battery and re-do the experiment? I am not sure if they will  trigger something in transit or not.

I tried on my bench. I couldn't re-produce your result at all.

Best Regards,

Linhong

Hi Linhong Qin,

I will try it, and give feedback to you soon. Thank you very much for your help.

Best Regards,

Phien Nguyen

Hi Linhong Qin,

I already removed all components that not related to the charge circuit, but it was still the same. Do you have any idea ? It's really a huge problem.

I hope to get some advice.

Thank you for any help.

Phien Nguyen

Hi Phien,

Thanks for the experiment. Battery voltage is very critical in charging control. Did you always have a Fluke meter in series in your setup? Can you remove it and try?

When a meter is put in series with battery, it adds IR drop etc to battery voltage, seen by our charger. Our charger will think battery is fully charged even though it's not. There are two ways I recommend try:

1. If you really want to know charge current, put a small resistor(eg. 0.01ohm) in series instead of a meter. Measure the voltage drop across the resistor and calculate current. Or,

2. Measure the voltage drop at charger's BAT pin and GND, instead of the real battery's. This is the "battery" voltage seen by charger. Make sure this voltage is well below your charge voltage limit.

Please let me know how this goes. Thanks.

Best Regards,

Linhong

BTW, in method 2, you can indirectly know approximate charge current by calculating from VBUS/I_vbus and Vbat, assuming ~90% efficiency.

Regards,

Linhong

Hi Linhong Qin,

I found that, when i changed bq27192 the limit charge current will be change (sometimes it's better, sometimes it's worse).

Thanks and Best regards,

Phien Nguyen

Hi Phien,

Are you able to do the experiment I suggested earlier? BQ24192 variation may play a role, but I think it would be minor in this case. Something else played a bigger role, which I suspect is VBAT voltage.

Thanks.

Linhong

Hi Linhong Qin,

I did it, and found that. When charge current is 400-600mA, VBAT very low (VBAT = VSYS - 50mV). Moreover, I found a set current value that VBAT will be not stable (charge current is also not stable and <= set current). If set current < this one --> maximum charge current (CC mode) = set current. if set current > this one --> charge current is only 400-600mA.

Best Regards,

Phien Nguyen

Hi Phien,

Which method did you use? with or without current meter in series?

What's VBAT voltage you read out? at battery or at BQ24192 BAT pin? Thanks.

Regards,

Linhong

Hi Linhong Qin,

I used a resistor in series (without the resistor or Fluke meter i got the same result). VBAT and VSYS i read at BQ24192 pin.

Thanks and Best Regards,

Phien Nguyen

Hi Phien,

I noticed your R174=270ohm for ILIM. This may be a little bit high for 2A charging. What if you use a smaller R or simply short it to GND and try? This will remove the limitation by ILIM.

Regards,

Linhong

Hi Linhong Qin,

I have more info for you. When charge current was 400-600mA, sometimes status showed not charging (charge current was continuous in the meter).

Best Regards,
Phien Nguyen

Hi Phien,

The other possibility is that we might have hit OCP limit. Our lower limit of this spec is 5.3A.  It is possible when higher current charging is enabled, charging current plus inductor ripple have exceeded that limit momentarily. IC was triggered to enter a protection mode.

To verify that, ideally we need to see the waveform of inductor current, with and without the problem. Are you able to get that?

To indirectly prove it, you can lower the input voltage or increase inductance. This should help push the "current fall-off" point higher.

Best Regards,

Linhong

Hi SamW,

I connected "to GPIO" to output of LM358 (comparison circuit with power supply: 12VDC).

Thank you very much.
Phien

Hi all,

Can I use 2 layer - PCB for bq24192 with charge current is 4A ? In the EVM it is 4 layer - PCB.

Thanks in advance,

Phien

Thank you very much  StevenB.

Best Regards,

Phien