BQ24040: PG signal behaviour doesn't match datasheet

Hi Dmitry,

Do you have a schematic I can look at to ensure everything is set up correctly? Can you show a waveform with measurements for the IN, BAT, and /PG where you observed p.2?

Hi Anthony, 

it's here. R11 is NC. CHG and PG pins are directly connected to the MCU inputs with internal pull-ups.

Unfortunately, it's hard to get a waveform right now. Do you have any ideas to investigate the issue further? 

Hi Dmitry,

We'll see what we can do with the information. Are you able to replicate this behavior if you don't use internall pull ups (if this is possible)? I also noticed that your  ISET resistor is 510-Ohms. We recommend putting it between 540-Ohm and 10.8-kOhm. Is it possible to increase this resistor value? 

What are the voltages when you see the issue for the following:

• TS
• OUT
• BAT
• IN (I know you said 5V in your initial post but would you be able to measure again when you measure the above?)

Hi Anthony, 

Thanks, we'll check different resistor values later. Should note that we have the same behaviour independently on ISET2 level for 100, 500 and resistor-based settings; still, the setting works fine - it changes chaging current as it should be.

Here some diagnostic info from gauge IC for reference:

internal temp.: 27.7C
temp.: 27.7C
voltage: 4118 mV
nominal available capacity: 984 mAh
Full Available Capacity: 1041 mAh
Full Remaining Capacity: 1046 mAh
Remaining Capacity Filtered: 1046 mAh
Remaining Capacity Unfiltered: 971 mAh
Full Charge Capacity: 1121 mAh
Full Charge Capacity Flitered: 1121 mAh
Full Charge Capacity Unfiltered: 1028 mAh
Average Current: -50 mA
Standby Current: -3 mA
Max Load Current: -226 mA
Average Power: -206 mW
State Of Charge: 94 %
State Of Charge Unfiltered: 95 %
State Of Health: 91 %, status 1

Voltages are:

IN = 5.005V

VBAT+ = 4.115V (could differ a bit from gauge report due to uncertainities and changing of current drawn by system)

TS = 0.522V

difference between OUT and system power (gauge input to output voltage): around 0.5 - 0.7 mV with steady state current drawn by whole schematic

Hey Dmitry,

Thanks for the information. It looks like charging is working properly. Is this issue seen on multiple units and is the observation reoccurring consistently? It sounds like you've already got this on a PCB is this correct?