BQ25606: BQ25606 STAT pin always remains low after first USB Power connect

Fahad Ansari20

Part Number: BQ25606

Hi,

We are using BQ25606 for a single cell 3.7V battery to manage power. I have got around 6-8 boards which are working fine

In one of the board, when I power up the board, the STAT pin remains high (due to 10k pull up) and once I connect USB power it goes low indicating charging started (till this the circuit is performing as desired). Now, when I disconnect USB power, the STAT pin still remains low. Even after reboot, this remains low. This goes high again only after I remove and connect the battery again.

I have used same battery on other board and the issue is not observed on those boards. I have tried changing the pull up resistor but still the same behavior.

Please suggest what things I can try.

over 6 years ago

0 Hong Mao over 6 years ago

TI__Expert 5590 points

Hi, can you check VBUS voltage after adapter is removed? Is the converter switching without adapter?

0 Fahad Ansari20 over 6 years ago in reply to Hong Mao

Intellectual 480 points

Hi Hong Mao,

The voltage at VBUS without adapter is around 4.6V

0 Hong Mao over 6 years ago in reply to Fahad Ansari20

TI__Expert 5590 points

Please measure both PMID voltage and VBUS. What is battery voltage in this case?

0 Fahad Ansari20 over 6 years ago in reply to Hong Mao

Intellectual 480 points

Before connecting the charger for the very first time, PMID voltage is 3.951V and VBUS is 0V

After connecting the charger once (even with the charger turned OFF or removed) PMID and VBUS voltage is 4.5V

Battery voltage is 4.18V

0 Joel Hernandez II over 6 years ago in reply to Fahad Ansari20

TI__Mastermind 25800 points

Hey Fahad,

You mentioned that PMID and VBUS are at 4.5V even when the input adapter is removed.

What is the state of the OTG pin?

Regards,
Joel H

0 Fahad Ansari20 over 6 years ago in reply to Joel Hernandez II

Intellectual 480 points

OTG pin is grounded in hardware (using 0E), it remains low

0 Joel Hernandez II over 6 years ago in reply to Fahad Ansari20

TI__Mastermind 25800 points

Hey Fahad,

Can you try adding a 1kOhm resistor to the input before you run your test, and then try it again?

Can you also describe your test set up? At what slew rate is VBUS removed? How much capacitance is on both the PMID and VBUS pin?

Regards,
Joel H

0 Fahad Ansari20 over 6 years ago in reply to Joel Hernandez II

Intellectual 480 points

Hi Joel,

Capacitors used are 1uF @VBUS and 10uF@PMID, I was not able to place the 1kOhm resistor between my USB connector and IC on my PCB (the power is routed in power plane, not accessible for rework)

I removed VBUS by plugging out my USB power cord, so there is no actual timing data available on this. I can try and find out the time delay in VBUS drop on VBUS removal using oscilloscope. Please let me know if there is any other parameter that I should check on oscilloscope.

0 Joel Hernandez II over 6 years ago in reply to Fahad Ansari20

TI__Mastermind 25800 points

Hey Fahad,

Our thought was to blue wire a resistor on VBUS to GND in order to see if it discharges the VBUS node.

As far as capturing on the oscilloscope, please capture the SW pin, VBUS pin, and VBAT pin.

Can you also tell us what the battery voltage is during this scenario?

Regards,
Joel H

0 Fahad Ansari20 over 6 years ago in reply to Joel Hernandez II

Intellectual 480 points

Hi Joel,

I soldered a 10k resistor between VBUS and GND and it resolved the problem, thanks a lot

However, I removed the resistor and tested again (for my curiosity) and it sometime shows the STAT pin high and sometimes low, should I go with the resistor placed in all the boards? (all other boards are working fine without resistor)

0 Fahad Ansari20 over 6 years ago in reply to Fahad Ansari20

Intellectual 480 points

Also, when the battery level reaches its maximum level (4.42V in our case) the STAT pin still remains high.
I checked the current on battery. Our system takes 60mA current. When there is no charger at max battery level, the current out from the battery is 60mA, when I connect the charger, this current goes down to 45/47mA.
From this, I feel that the charger is providing remaining 13/15mA of current and hence the STAT pin remains high, I have added a 10K resistor between VBUS and GND but same result. Please help resolving this as well

0 Fahad Ansari20 over 6 years ago in reply to Fahad Ansari20

Intellectual 480 points

Another observation
When I switch OFF the module, the battery current goes to zero and the stat pin goes low, now when the module is turned ON, the STAT pin remains low. If I reinsert the charger, the STAT pin goes high again and stays high unless the module is turned off.

0 Joel Hernandez II over 6 years ago in reply to Fahad Ansari20

TI__Mastermind 25800 points

Hey Fahad,

I would keep the 10k between VBUS and GND on every board.

Regards,
Joel H

0 Joel Hernandez II over 6 years ago in reply to Fahad Ansari20

TI__Mastermind 25800 points

Hey Fahad,

As your 2 replies are different questions from the original question about VBUS when the STAT pin goes low, can you please open a new thread with those questions?

This improves the search results for those looking for similar answers.

Regards,
Joel H

0 Fahad Ansari20 over 6 years ago in reply to Joel Hernandez II

Intellectual 480 points

OK Joel, I'll do that, thanks for the help

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BQ25606: BQ25606 STAT pin always remains low after first USB Power connect