BQ27510-G3: GPOUT to disable charger

Wyatt,

I agree PFC to be correct.  So when the GPOUT_INT is set to "BAT_GD" does that mean it uses the PFC bits?  Right now it is configured as follows:

GPOUT_POL = 0

GPOUT_INT = 1

BATG_OVR = 0

BAT_FN 0

I think i needs to be

GPOUT_POL = 0

GPOUT_INT = 0

BATG_OVR = 1

BAT_FN = 1

Can you confirm?

Also it seems like I need BATG_OVR on so that if the pack goes to a low voltage (not good?), the fuel gauge will still enable charging.  Again this isn't explained very well in the datasheet.

Hello Andrew,

Let me check with someone that has more experience with this gauge, the TRM has a complex way of explaining this pin.

Sincerely,

Wyatt Keller

Wyatt,

Thanks.  I'll wait for your reply.  

My best guess is that I need to do the following, but it remains still a bit unclear on whether this ONLY makes the pin go high when the pack is too hot or cold.  This also assumes the inputs to the "batt good" calculation are the battery pack temperature.

OpConfig_D

SOC_STATE = 0

SOC_OCV = 0

SOC_DFW = 0

SOC_OT = 0

OpConfig

INT_BERM = 0

PFC_CFG1 = 0

PFC_CFG0 = 1

GPOUT_POL = 0 (active low,  charger is enabled when CE is low)

GPOUT_INT = 0   (bat low or bat_gd)

GPOUT_FN = 1 (bat_gd function)

BATG_OVR = 1

OpConfig_B

BL_INT = 0

RMC_IND = 0

Wyatt,

This appears to be working at first glance, however when the battery gets discharged to low voltage, the pack protection turns off the discharge FET and prevents a battery voltage from being present.  This seems to be causing the fuel gauge to continue to keep GP_OUT high.  How do I work around this?

Hello Andrew,

Can you send your .gg file so I can see your configuration? Do you want the protections to be triggered? Or is the issue just the GPOUT is staying active while the protection is on and the FETs are off, but you want the GPOUT to be de-asserted when the protections are on?

Sincerely,

Wyatt Keller

GPOUT is pulled up to 5V USB essentially.  The logic was it only needs to be pulled up when a charger is present.  The issue is that the BQ25895 is disabled by GPOUT being high when there is "no battery" either because there is no battery or the battery pack electronics have shut the discharge fets off.  So when this happens GPOUT is preventing the BQ25895 from charging.  

Should GPOUT be pulled up to REG25 on the BQ27510 instead?

Golden image is attached.goldenimageGPOUT.zip

Pulling GPOUT to VBAT doesn't seem to help. The charger outputs ~2V with significant ripple on it and GPOUT is still high.  I'm not sure why it won't just start.

When I used to use this part with a separate thermistor for the BQ25895 and no GPOUT pin connected to CE on the BQ25895, the charger would always start up even without a battery inserted.  I changed to this configuration because I like the idea of using the actual battery pack thermistor that was connected to the fuel gauge to enable and disable charging.

Hello Andrew,

I think you sent the flash stream files, you can generate the .gg file from the data memory tab and using the export function.

So the GPOUT is still staying high and preventing the charge, but now it's only when the FETs are off? You should be able to configure the gauge so the FETs don't turn off when you're still trying to charge if this is the problem.

Sincerely,

Wyatt Keller

Sorry, see attached.  The issue is that when there is no battery attached or where the battery pack built in electronic protection turns off the discharge FET in the pack (discharge protection), there is no battery voltage present and so GPOUT is high and disables the charger.  The issue is the pack is waiting for a charge to raise the pack voltage above 3V so it can turn the discharge FET back on.  However, the BQ27510 GPOUT is keeping the charger off.  There is no way for the unit to get out of this state because the charger stays off because the fuel gauge thinks there is not battery and so GPOUT stays high and the charger is sitting there waiting to enable the discharge FET again, but it won't until the charger can raise the battery voltage to a reasonable level.

0334.files for ti 2.zip

Hello Andrew,

Thanks for clarifying, I understand better now. Let me look through the .gg file tomorrow and get back to you then.

Sincerely,

Wyatt Keller

Hello Andrew,

I've been researching your issue, it doesn't appear to be a gauge problem if it is working correctly without the pack safety shutting off the discharge. With the current configuration the gauge should only trigger the charger to shut off when outside of the temperature range specified. Is the temperature hysteresis having an effect when the charging is stopped and then is starting again? 

Are you testing on an EVM where you can log the data with an EV2400 and bqStudio?

Sincerely,

Wyatt Keller 

It works fine when the pack protection isn't turned on.  I was thinking about this more and the only way I see to fix it is to add a N-Mosfet to act as in inverter.  Then invert the GPOUT polarity in the golden image.  This way when the fuel gauge isn't powered and GPOUT is high impedance, the charger is enabled.  Once the charger wakes up, it can then take control of the pin as appropriate.