BQ25672: BQ25672 OTG with one valid VAC Input

Hi Pascal,

With external back-to-back FETs with gates driven by ACDRVx pins and inputs sensed by VACx pins, you can have 2 input sources and then put OTG on either VAC1 or VAC2.  Enabling OTG is a 2 step process 1) set the EN_OTG bit (REG0x12b6) = 1 and then enable VACx with ACDRVx bits in REG0x13.

Regards,

Jeff

Hi Jeff,

Thanks for the answer .

I would like to clarify my topic.

My problem comes from the ORED  input VBUS pin which can be selected either from Vin1 or Vin2. So ACCDRV1 and ACCDRV2 cannot be active simultaneously.

In my design Vin1 is a regulated 5V supplied by a 12V vehicule battery . Vin2 is an USB2.0 port.

When Vin1 is connected to 12V battery, Software may be able to provide 5V to USB port Vin2 for OTG functionnality even if battery is totally discharged or disconnected.

I see 2 solutions but I am not sure they are possible, please check or propose another configuration:

1. Desactivate ACCDRV1, enable internal OTG ( if it can be supplied by VAC1 input pin), activate ACCDRV2 to provide 5V VBUS on VIn2 USB port.

2. Desactivate ACCDRV1, configure BQ25672 to provide on VBUS a 5V coming from Vin1 without internal OTG functionnality, activate ACCDRV2 to provide 5V VBUS on VIn2 USB port.

What is the true input pin VAC1/VAC2 or VBUS?

Is it possible to provide a 5V on VBUS as output pin when Battery is totally discharged or disconnected?

Regards,

Hi Pascal,

The charger either runs in forward/charge mode OR reverse/OTG mode, not both at the same time.  OTG mode is powered from the battery.  VACx pins are for sensing voltage only and do not provide power.  So....

Regarding 1, except for the statement about VAC1 suppling anything, if the battery is charged, this should work.

Regarding 2, this will not work.

Regarding,

Jeff

Jeff,

Ok understood. That is what I was afraid of.

Regarding1 , battery will be the active source for OTG function so for my requirements ( battery totally discharged or disconnected) it will not work. Correct?

My only solution is to add an external back-to-back dual mosfet between VIN2 (USB port) and VBUS pin controled by software. This circuit should only be activated when VAC1 is deteced, Battery is discharged or removed.

Regards,

Jeff,

In datasheet 8.3.7.1 OTG Mode to Power External Devices , we can read :"The following cases explain the charger OTG mode behaviors when the ACFET1-RBFET1 or/and ACFET2-
RBFET2 are present.
• If only ACRB1_STAT=1 OR only ACRB2_STAT = 1, which means only one input ACFET-RBFET is present,
the converter stays in the non-switching mode after the EN_OTG bit is set, until the host writes EN_ACDRV1
= 1 (when only ACRB1_STAT = 1) or EN_ACDRV2 = 1 (when only ACRB2_STAT = 1). The converter starts
up with 5ms delay after the EN_ACDRV1 or EN_ACDRV2 bit is set to 1, then VBUS voltage ramps up to the
VOTG register setting."

If VAC1 is detected (ACRB1_STAT = 1), if  EN_OTG bit is set and after the host writes EN_ACDRV1= 1, I suppose VBUS pin will follow VAC1 and they will be a conflict if VOTG converter starts as explained. Do you agree or please clarify.

Regards,

Hello,

I will get to your question later this week.

Thanks,

Mike Emanuel

Hello,

OTG mode is powered from the battery.

If I have VAC1 plugged in and the battery plugged in, I charge in the forward mode. If I enable OTG, the converter continues running in the forward mode. If I then disable charge, VBUS remains at the VAC1 voltage. If I remove VAC1, VBUS reaches the OTG voltage.

Thanks,

Mike Emanuel

Please click "Resolved" if this answered your question.

Hello,

I replicate your scenario, it is OK on my EVB.

I understood OTG is not active when either VAC1 or VAC2 is present.

OTG source can only be the battery