TPS25751: PP5V requirement for Sourcing (USB OTG)

Hi Aya Khedr , 

Thanks for the quick response! This does sound like a deal breaker for me as a very low power requirement is required for my 1S application. I would like to avoid any other boost circuitry if possible other than the one internal to the BQ charger -> TPS25751. 

Are there any better solutions from TI that gets around this of supporting a USB PD solution optimised for a 1S application?

It is perhaps possible to NOT provide any supply on PP5V if i am just doing only implementing a USB sink application (which means that the CC lines does not have to be powered) and provide 5V USB OTG (USB 2.0) through the BQ battery charger?



Kind regards, 
rimark

Hi Aya Khedr 

Its good to know that for sink application PP5V is not needed!


Regarding my questions on providing 5V on VBUS as a USB OTG host for another device that only requires 5V with USB 2.0. Can I get clarity that this is still okay to source this standard USB 2.0 power spec without the need of PP5V as the only communication required enumeration through D+ and D-? Or does the PD controller stop this from happening? Can I somehow go direct to the BQ charger D+ and D- line ?

Sink Application: USB PD 5V, 9V @3A
Source Application: USB 2.0, 5V  @0.5A

Deeply appreciate your time otherwise on this as I really want to stick with this TI architecture solution in hand!


Kind regards,
rimark

Hi Rimark, 

I'll need to check with the BQ team and get back to you. Could you provide a block diagram with your suggestion? 

Best Regards, 

Aya Khedr

Hi Aya Khedr ,

I have made some edits on the original TPS2571D Block Diagram from the datasheet. Do let me know what the BQ team thinks of this!

Kind regards, 
Rimark

Hi Rimark, 

Thank you for sharing. I will review with the team and get back to you. 

Best Regards, 

Aya Khedr

Hi Aya Khedr , having further read up about this, the architecture above may still pose some challenges.
DP and DN enumeration with the BQ charger with the USB OTG peripheral device will not work unless it is already receiving power from VBUS to begin with. 

The only way that it is possible for me to implement this to brute force the BQ and TPS25751 to enable VBUS by default but from my understanding this will violate the USB Type-C specifications. Normally it will be the CC lines or ID pin (if microUSB connector) that needs to signal the USB OTG host to enable VBUS. I have seen other solutions where the microcontroller has a UCPD peripheral to drive the CC lines which only required 3V3. 

For a 1S application, having that separate boost converter for PP5V just doesn't fit my requirements for space constraints and maintaining a low power consumption (high efficiency power management system). 

 

Hi Aya Khedr  ,


Deeply appreciate your help verifying this. Could you perhaps provide an indication on how much current I would need to separately provide for PP5V for just the CC logic before i switch over to the main PPHV when boosting from BQ charger. I would like to further explore small current boost converters to see if I can still meet my power efficiency and space goals. 

Thank you!
Rimark

Hello Rimark,

Please be advised that Aya is out of office today. You may experience delay in receiving a response.

We appreciate your patience. 

Thank you,

Katilynn