• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 32 subscribers
  • Views 1362 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.

TUSB320LAI: Battery charger IC selection for USB2.0 OTG --> USB-C revamp

Vikram Godbole
Prodigy 90 points
Part Number: TUSB320LAI
Other Parts Discussed in Thread: BQ25606, TUSB320

We are trying to design a USB-C compliant system with USB2.0 OTG functionality. The requirements are as follows:

  1. Fits within USB-C native power profile (15W). USB-PD not needed.
  2. Device will be a DRP, with a Try.SNK preference when connected to another DRP.
  3. Battery must charge at 3A when connected to dedicated charger. Device can be powered on or off while charging.
  4. When connected to a DFP, must charge at the current capacity indicated on CC pins.

Based on the couple of USB2.0 -> USB-C transition whitepapers on the TI website, we picked the TUSB320LAI as the CC controller. We are considering the BQ25606 as the battery charger. However, there are some issues with this:

- In order to configure the TUSB320 as Try.SNK, it must be operated in I2C mode. And when in I2C mode, presumably the system processor needs to read TUSB current mode via I2C and then switch the Rlim current-limiting resistors on the battery charger IC. But what happens if the device is off while charging? Somehow the current mode still needs to be conveyed to the battery charger. I assume this could be done via levels on the GPIO OUT pins - which means that the TUSB must be in GPIO mode. However, when the device is on, the TUSB320 definitely needs to be in I2C mode. So - can the TUSB mode be switched dynamically, from GPIO (when device powered off) to I2C (when device powered on)?

- The BQ25606 appears not to be an appropriate charger anyway, since it sets input current limit per Dp/Dn levels, according to the BC1.2 spec. When a DCP is detected (with Dp/Dn shorted) it limits charging current to 2.4A. So we cannot avail of the full 3A native capability of USB-C. Is there a charging solution that will set up charging current based on current mode detected on the USB-C CC pins? 

 

 

  • 0
    TI__Genius 16150 points
    Hi Vikram,

    The TUSB320L/H supports dead battery mode. Basically in this mode, the device has enabled Rd pull-down resistors on CC pins to charge the battery. The scenario that you are mentioning is not feasible, since when the system is OFF (VDD=0), the TUSB320 will be conveyed the default current level. Once the system has a valid VDD level, the I2C registers can be read out to adjust the different valid current levels. Hence, in dead battery mode, the TUSB320 is OFF, even in GPIO OUT1/OUT2/OUT3 does not work, until the VDD is valid the device if going to enable these output signals or I2C registers.

    Best Regards,
    Luis Omar Moran
    High Speed Interface
    SWAT Team
  • 0 in reply to Luis Omar Moran
    Prodigy 90 points

    Thanks Luis. Ok, I now understand the dead battery mode operation, but in most cases, the battery won't be completely dead, it will just be discharged. If we then connect VDD directly to the battery as shown in this diagram (from the "Low-cost USB-C Implementation" whitepaper) then TUSB320 does have valid VDD. In this case is it possible to detect and enable fast (3A) charging? Assume the rest of the system is still powered off (so I2C is still not possible). 

    I understand that it is not a full-fledged schematic, but the battery charger block in this diagram is not shown to have any interface to the CC pins (or to the TUSB, or to the processor). In a USB-C system, how is the charger expected to figure out charging current capacity?

     

  • 0 in reply to Vikram Godbole
    TI__Genius 16150 points
    Hello Vikram,

    In GPIO mode, the TUSB320 only advertises default Type-C current level. If your application needs a higher current level I2C is mandatory. As well, the Try. SNK and Try.SRC are specific features for I2C mode.

    Regards,
    Luis
  • 0 in reply to Luis Omar Moran
    Prodigy 90 points

    Luis Omar Moran said:


    In GPIO mode, the TUSB320 only advertises default Type-C current level. 

    Would you clarify this some more? Per Table 3 in the datasheet:

    Isn't the "Attached" state determined only by VBUS detection? So if connected to a charger-only source, will the TUSB not be in the Attached state? (And if it is, it ought to indicate the current level in GPIO mode?)