BQ24610: False Charge Complete

Cody Benson

Part Number: BQ24610

I have developed a custom board with the BQ24610 to charge a 4 cell li-ion battery. The schematic is shown below. Note that I have depopulated R49 so there is no external load on the battery. Also, BAT- is connected to a 0.1 Ohm GND to incorporate a fuel gauge that is currently not shown and is DNP. Lastly, there are 30k pull-ups for CE, STAT1, STAT2, and PG that are not shown on this page. Ultimately, the issue is that when I have the DC power applied and a battery connected, I am seeing CE on, STAT1 off, STAT2 on, and PG off which indicates a charge complete state. I would expect to see STAT2 off so that it is in the charge state as my battery voltage is at ~13.2V. Do you see any issues with the schematic, or can you think of any reason why it may not be charging? Here are relevant measurements that may be of interest:
Power Supply - 24V, Battery: 13.2V, ISET1 - 182mV, ISET2 - 94 mV, ACSET - 528mV, VREF - 3.27V, REGN - 5.97V, VFB - 1.52V, and TS - 1.68V.

over 2 years ago

0 Michael Emanuel35 over 2 years ago

TI__Mastermind 40305 points

Hello,

Can you please confirm your measurements? I am calculating full battery charge voltage at 16.758 V. The battery voltage that would correspond to a 1.52 VFB is 12.13 V. Currently we are seeing a battery voltage of 13.2 V which corresponds to a VFB of 1.65 V.

Regards,

Mike Emanuel

0 Cody Benson over 2 years ago in reply to Michael Emanuel35

Prodigy 10 points

I used a better DMM and the battery voltage was 13.17V and VFB was 1.64 which is correct. I calculated the same charge voltage as shown in the schematic notes.

0 Michael Emanuel35 over 2 years ago in reply to Cody Benson

TI__Mastermind 40305 points

Hello,

Can you please explain this 0.1 Ohm in the battery path? Have you measured from SIG_GND to VFB? What happens if you switch devices?

Regards,

Mike Emanuel

0 Cody Benson over 2 years ago in reply to Michael Emanuel35

Prodigy 10 points

The 0.1 Ohm is for low side current measurement, and it is not currently used (shorted to HV_GND). SIG_GND and HV_GND are tied thru the center pad of the charge controller as suggested in the layout guidelines, note 7 in the datasheet. I have not yet tried another part as it will involve rework.

0 Michael Emanuel35 over 2 years ago in reply to Cody Benson

TI__Mastermind 40305 points

What is the VCC voltage? Can you provide a waveform of VCC, PH, SRN and charge current?

-Mike Emanuel

0 Cody Benson over 2 years ago in reply to Michael Emanuel35

Prodigy 10 points

VCC is 24V. I do not have a current probe to get the charge current on my scope. Attached is a zoomed in waveform for VCC, PH, and SRN. Do you want to see something at start-up or steady-state as shown? I do have a DMM connected and there is 12.82mA being discharged from the battery. STAT2 is still high so it is not charging.

0 Michael Emanuel35 over 2 years ago in reply to Cody Benson

TI__Mastermind 40305 points

Hello,

Are you sure the battery is connected properly? A battery is a solid DC voltage source and should not oscillate like the shown SRN waveform.

Regards,

Mike Emanuel

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BQ24610: False Charge Complete