• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 1185 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Advice on bidirectional power bank ICs

Nicolas Venturo
Intellectual 810 points
Other Parts Discussed in Thread: BQ25895, HD3SS3220, CSD25310Q2

Hello,

We're currently designing a product using a BQ25895 that acts like a power bank: the system has a battery that can be charged from VBUS (an input micro USB connector), and 5V can be supplied from the PMID pin (an output USB A connector). I am now wondering if TI has any chips that can be used with a bidirectional USB Type-C connector, that would allow the system to both be powered and supply power using the same connector. There is no need to implement USB PD, since high voltages (over 5V) are not required.

I've been reading a bit about chips like the HD3SS3220, but it looks like that IC has no power features, just the signaling and data multiplexing (which I don't care about, the differential pairs will not be connected to anything on my system).

Thanks!

  • 0
    TI__Expert 8230 points

    Hello Nicolas,

    Please review the reference design PMP4496, which I believe encompasses what you are looking for...The design uses the bq25895 for fast charging and includes the ICs that handle the role detection of the Type C connection to determine when it needs to behave as a source or a sink to provide the boost output.

  • 0 in reply to Fernando Lopez
    Intellectual 810 points

    Thank you very much Fernando! Indeed, it looks like that reference design could be a very good starting point. I have some questions about it however, but I'm not sure if this is the correct place to ask them.

    My questions are:

    a) Why is the TPS61235 (5V 3A boost power supply) used? The BQ25895 is capable of delivering up to 3.1A at 5V on the PMID pin, so I am not sure why this IC was chosen.

    b) While charging an external device, what prevents the BQ25895 from charging the battery from the voltage on VBUS, after TPS61235 turns on and VBUS and 5V_SYS are connected?

    c) What is the porpuse of the Q2/Q3 circuit? I understand that Q1 and Q4 disconnect VBUS from 5V_SYS while charging the battery , and they connect them together when discharging the battery, but the rest of the circuit doesn't make sense to me. If Q2 is a p-channel MOSFET, won't that prevent current to flow from 5V_SYS to VBUS to discharge the battery?


    Thanks!

  • 0 in reply to Nicolas Venturo
    TI__Expert 8230 points

    Hello Nicolas,

    While the bq25895 can provide an OTG output at PMID, a powerbank application for this would require 2 USB ports, one for input and the other for output. The output of the OTG on the bq25895 is on the PMID pin and the reverse block FET will turn off to ensure the OTG output is not seen on VBUS. The TPS61235 offers better efficiency at 3A than the 895, hence why they went with a separate boost stage.

    Also, the 2x CSD25310Q2 FETs between VBUS and the output of the boost converter are controlled by the host according to the result from the type C identification ICs. This ensures both are not trying to output to the same node.