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BQ76PL455A-Q1: VP pin and question about daisy chain

user6002568
Prodigy 40 points
Part Number: BQ76PL455A-Q1


Hello,

I have some question about design for this BQ76PL455A-Q1 IC.

1. VP pin：this pin is for internal regulator(A/D), can I use this pin to another IC that the supply current is about 10 mA ?

2. In Daisy Chain structure, VIO pin should connected to the VDD pin which is belong to the MCU.

    Is this design for the transmission of TX、RX、WAKEUP、FAULTN signal ? If yes, can I use an isolation IC to transport these four signals, and leave the VIO pin and VDD pin be separated?

3. The use of our product is cell monitor in Automotive, so we should design like the Figure.34 in the spec., how to choose the value of common mode filter、isolation capacitor、resistance ?

By the way, I want to know is there any practical applications on Daisy Chain for Automotive battery monitor about this BQ76PL455A-Q1 IC?

Look forward to your reply as soon as possible, thank you. 

  • 0
    TI__Intellectual 2520 points

    Hello,

    Thanks for choosing bq76pl455.

    1)You can use VP to supply another IC. Please connect VP to another IC by 1ohm resistors, like VDIG and VIO.

    2)Yes ,you are right. But when you use an isolator, you should also connect isolator's power(455 side) to VIO.

    3)You can access 455 pages in TI website and you can fins many app note. I attach design app note for your reference.

    Andy

    SLUA791_bq76PL455A Design Recommendations.pdf

  • 0 in reply to Andy Li55
    Prodigy 40 points
    Hello,
    Thanks for your reply.
    1)2) Actually, the IC which I want to connect to VP in question 1 is the isolation component we talk in question 2.
    So, it says that I could directly connect isolator's power(455 side) to VIO?
    3) I have read the reference, but I want to know in Figure.34 there are some recommend design like：
    10 ohm、470uH、100uH、1nF、5V TVS, where I can get more detail descriptions, or just try and error experience from your team so we
    could only design the same with you?
    4) Another question is GPIO pin, are they use for judgment the information is from which stack?
    5) I want to double check the design between single-ended and daisy chain(master), I found some difference below:
    a. Connect the VIO pin and VDD pin: the question we discuss in 1)2).
    b. COMMH+、COMMH-、FAULTH+、FAULTH- pin should connect to mid stack.
    Only these two different? Am I correct?
    Look forward to your reply as soon as possible, thank you.
  • 0 in reply to user6002568
    TI__Intellectual 2520 points

    Hello,

    1)You can connect VP to VIO for all stack 455, but for the base 455, since it will communicate to host by isolator, so the power of isolator should also supply

    base 455;

    3)You should pick components as close as recommendations.

    4)Just GPIO. wakeup pin is used to judge stack or base.

    5)The direction is base's COMH to stack's COML, and then stack's COMH to next stack's COML.

    Thanks!

    Andy

  • 0 in reply to Andy Li55
    Prodigy 40 points

    Thank you, Andy.

    So I want to design like below:

    Directly connect VIO pin to the isolator's power(455 side) on the base 455 for two use.

    1. For single-ended: transmission TX、RX、WAKEUP、FAULTN signal.

    2. For daisy chain(master): transmission the stack information.

    Is that OK?

  • 0 in reply to user6002568
    TI__Genius 10785 points
    Hi User,

    you can't do that. VIO is shutdown until you wake up.
    So, you won't be able to wake up the device because one side digital isolator is not powered.
    So, you have to use separate transformer for wakeup pin.

    Does it make sense?

    Roger