ACOK at BQ24728 DA0R53MB6E0 issue

[rookieme]

Hello team,
I'm having issue with ACOK signal at BQ24728.
The notebook is able to work with battery but with power adapter only blinks 3 times at dc in when power button is pressed.
I managed to find that ACOK is missing from BQ24728,
so far I have replaced it with BQ24735, replaced the KBC, checked the dc in mosfets and currently I'm out of ideas.
Any help will be appreciated.

[lapfix]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Why you replaced BQ,KBC without taken voltages before!
Start with taken the requirements voltages for BQ to work : Pin 20/6/16 and post it here

[RethoricalCheese]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Have you checked if middle pin of charger is functioning properly?

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Thank you for replying,
voltages at BQ p20=19,5V, p6=2,68V & p16=6V
they seem normal to me

The adapter ID pin has been messured ok all way to kbc.

replacing parts seemed to me the only way to figure it out...

[stingerchamp]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Hi,

Can you share what is the voltage on cmsrc and ad-id?

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

BQCMSRC is 19,5V and AD_ID is 0,77V measured at C737

[qayyum786]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

what is your gate voltage on PQ46 & PQ48

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Nice question, PQ46 gate has 17,62V and PQ48 has 24,58V

[kadi144]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

same problem ACOK =0v

therefore i have changed the bq
https://www.badcaps.net/forum/showth...ikosalalalal33

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

already done that but problem remains

[emestee]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

ACOK you mean ACPRES? Pin 5? If so then: ACPRES is pulled up from the charger's LDO (pin 16) via PR80. So, you're saying that you have 6V on the left side of PR80 (=REGN6V) and 0v on right side (=ACPRES). ACPRES is open drain (meaning that the charger does not push voltage on that pin when it needs to be high, only that it shorts it to ground when it needs to be low; the voltage of the high level must come from elsewhere). If the resistor doesnt pass REGN6V voltage, the pin will remain in floating state. Measure PR80 resistance.

[ktmmotocross]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

check first two mosfet if not shorted

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

non of them is shorted onboard
I haven't removed them though to test if the work properly

[emestee]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

non of them is shorted onboard
I haven't removed them though to test if the work properly

Did you test PR80 like I wrote?

[qayyum786]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

non of them is shorted onboard
I haven't removed them though to test if the work properly

what is the impedance of pin 5(ACPRES) of pu8 ?

[qayyum786]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Nice question, PQ46 gate has 17,62V and PQ48 has 24,58V

both gate voltages is fine as per R53 mbd

[mcplslg123]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

PQ11 populated on mb??PU12 pin15 resistance??

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Did you test PR80 like I wrote?

Yes it is measuring about 83K onboard, one side 6V and the other 0V

from datasheet: ACOK AC adapter detection open drain output. It is pulled HIGH to external pull-up supply rail by external pull-up resistor when
voltage on ACDET pin is between 2.4V and 3.15V, and voltage on VCC is above UVLO and voltage on VCC pin is
275mV above voltage on SRN pin, indicating a valid adapter is present to start charge. If any one of the above
conditions can not meet, it is pulled LOW to GND by internal MOSFET. Connect a 10kΩ pull up resistor from ACOK to
the pull-up supply rail.

So ACDET pin has correct voltage.
Also pulled high trough PR80.
VCC pin is much higher that SRN pin.
VCC above UVLO? What is the UVLO?

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

what is the impedance of pin 5(ACPRES) of pu8 ?

It is about 65K

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

PQ11 populated on mb??PU12 pin15 resistance??

PQ11 is missing - it seems it was never there.
PU12 pin 15 has about 65K