BQ25606: BQ25606 :: after charging completed -> STAT pin is still LOW

Measured voltages:
Vbus=4.896 V
Vpmid=4.846 V
Vregn=4.786 V
Vts=2.76V
Vbat=3.85V

USB_DP and USB_DN are floating (because charger is connected directly to dc power supply), OTG pin is LOW.

Added:
I tried to connect charger to USB port of PC. Charging current is limited at 500 mA, so device is successfuly recognised as USB device, but after charging ends, STAT pin is still LOW.

Hello,

I tried to connect a 1k resistor between VBUS and GND, but this doesn't solve a problem.
Any ideas?

In connection with attached schematic (one post up) I must say that resistor R20 is not placed, so OTG pin is connected to the ground.
On the USB_DP and USB_DN lines, a FT232RL is connected (it has 1.5k pullups integrated on both lines) but I think that this is not a problem, because a BQ25606 charger recognition works normaly.

Many thanks,
BR,
Dejan.

Hello Joel,

if I understand right, the charger is in VINDPM mode when the VBUS voltage is higher than VBAT+300mV, and I can confirm that for my example is. But this is normal situation for a charger? Also when the battery is full (approx. 4.208 V) and external power supply is still conected, VBUS is still higher than VBAT+300mV.
For TS a 103-AT NTC resistor (10k) is used and its temperature is around normal room temperature. Measured voltage on TS pin is around 2.76 V, Vregn is around 4.786V, consequently the V_TS/Vregn is around 57.7%.
IIINDPM - > For I_LIM resistor a 220R resistor is used. That means that I_LIM is around 2.27A. I'm using external DC power supply - 5V and I'm not sure but it could be possible that I used 2A for a current limit (I will try tomorrow with 3A current limit on power supply), so this could mean that charger was out of full funcionality. But I'm sure that charger sinks around 1.4A which is completly connected with resistor chosed for I_CHG (current from charger to battery) which is 470R.

Thermal regulation: IC doesn't became hot, so I think that this is not a problem.

Any idea what can I also check or try (tomorrow I will check used current limit of used DC power supply)

Many thanks!

In table on page 9 in datasheet I can read that also if the charger is recognised as USB device, USB input current regulation limit is activated. I can confirm that this recognition works in my example, but - does this also means that (if USB port of the computer is used as power source) charger will not terminate?
I'm not sure if I understand a behaviour of this BQ25606, I don't understand which conditions must be achivied for sucessfuly termination of a charger.
My idea is to use an unknown charger to charge a battery and also a USB port of PC. In both examples I would like that BQ25606 gives me an information when charging is completed (STATE pin must go from LOW to HIGH), but I don't understand how to achieve this.

Many thanks,
Kind regards,
Dejan.

Hello,

I tried to use non-standard charger - DC Power Supply (5V with 5A current limit), but current from power supply is still limited to around 1.45A, which is not current set by I_LIM resistor (approx. 2.27A) but current set by I_CHG resistor (470R -> 1.44A). If power supply is not poor (it can provide adequate current - set by R_LIM) but is limited by R_CHG resistor, does this mean that charger is also in IINPDM mode?
Or maybe charger in my example is not recognised as unknown adapter? - I have FT232 IC connected in parallel to D+/D- lines, so this can confuse charger. How can check for sure if charger recognise my external power supply as unknown supply - as I said it is for sure unknown adapter (D+/D- are not conneted by outside device, except of FT232 IC which is on the same PCB)?

Many thanks,
BR,
Dejan.

Hey Dejan,

You can confirm this by removing the R87 and R88 0-Ohm resistors on in your schematic and re-running the test.

Can you also measure the VAC voltage (at the pin) and BAT voltage (at the pin) when the charge current becomes <10mA)? If you try with the test with a 9V power supply, we can eliminate this possibility. 

And is the STAT pin pulled low even when the /CE pin is pulled HIGH?

Regards,

Joel H

Hello Joel,

I removed R87 and R88 and after that I re-run the test. Current from 5V power supply to the battery is still around 1.4A. It looks like that this current is determined by R_charge resistor and not with R_lim resistor?

I can't try the test with a 9V power supply because of many other electronic components which are also supplied from 5V line :(

When the charge current (current from BQ25606 to the battery) drops below 10 mA, V_VAC = 4.982 V and V_BAT= 4.194 V

During charge process if I toggle pin /CE from LOW to HIGH, current from power supply drops under 50 mA, but STAT pin still remains LOW.

Thanks,
BR,
Dejan.

Hello Joel,

now I measured also a current from a battery to the BQ25606, when VBUS=0 V...It is around 4 mA!!
What do you think - It is possible that I have a faulty IC?

Thanks!

Hey Dejan,

Something seems off. Not sure if it's with the IC or not. However, if the /CE pin is pulled HIGH, the STAT pin show not stay low. 

Have you tried with a new IC?

Regards,

Joel H

Hello Joel,

I tried with other IC but the problem still persist. I don't have any other idea what could be wrong. In next week or two I will prepare PCB with the same IC but with some minor changes (capacitor on input, resistor on V_SET, ...) ...I will let you know if this will help in any way.

Thanks for all!

Hey Dejan,

Can you also try tying the D+ and D- pins of the charger together? I want to see if the input source detection is playing a role. 

Other than that, can you change the pullup on STAT from 1k to 10k?

Regards,

Joel H

Hey Dejan,

Were able to try my suggestions in the previous post?

Regards,

Joel H