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BQ76PL455A: BQ76PL455A-Q1 - Master Slave configuration

Suriyaprakasam Chinnusamy
Prodigy 100 points
Part Number: BQ76PL455A
Other Parts Discussed in Thread: ISO7742,

BQ_Battery Monitoring_Master& Slave configuration.pdf

Hi,

We are developing 300v battery management system for EV Application in our design BQ Series(BQ76PL455A-Q1) battery monitoring ic is used for sensing and monitoring.

i have clarification in the master and slave configuration in our case master board contains micro controller and 2 slave board contains total of 6 Battery monitoring ic's as shown in figure.

All the battery monitoring ic's are connected in daisy chain configuration please, refer below figure and confirm the configuration. if it is correct which one would you suggest either CAN or RS 485?

Please let me know if any other clarifications are required.

Thanks for your support

  • 0
    TI__Genius 11480 points
    Hi Suriyaprakasam,

    Overall, the stacking of the pl455 looks good. This is the typical use case.

    I think you may want to consider some changes to your master/CAN configuration. Without knowing your system configuration, i can only offer ideas.

    If seems that you would need a CAN Controller, as well as the CAN transceiver in your set up. To my knowledge, a CAN transceiver will not translate from CAN -> UART or UART-> CAN.

    One alternative will be to isolate the UART directly. Another option would be to isolate CAN to the MCU (possibly moving the MCU to the slave board), and connecting MCU UART to the pl455. You may be interested in the pl455 use case document : www.ti.com/.../slua785.pdf
  • 0 in reply to David Wiest Jr
    Prodigy 100 points

    BQ_Battery Monitoring_Master& Slave configuration.pptx

    Hi David,


    Thanks for your reply.

    yes. i agree your point we should have been used can controller along with transceiver.

    In other way we could not able to move micro controller to slave board because of other peripherals present in the master board.

    Could you suggest  ISO UART Part No for direct interfacing with micro controller?

    Thanks & Regards,

    Suriyaprakasam C

  • 0 in reply to Suriyaprakasam Chinnusamy
    TI__Genius 11480 points
    Hi Suriyaprakasam,

    I have used the iso7342 (the newer , improved version is iso7742 i think). As long as it matches your needs for data rate, isolation rating, power consumption, and forward/reverse channels (pl455 needs 2 forward, 2 reverse for TX,wakeup, and RX, faultn), it will be acceptable.
  • 0 in reply to David Wiest Jr
    Prodigy 100 points

    Hi David,

    Thanks for support and suggestions.

    Yes. We can use same isolator in our design it almost matching all the requirements but still I have few clarifications on the master slave configuration.

    As I mentioned earlier in our design microcontroller will be in master board and bmu unit in slave board.

    1)How to control the external noises if we use uart (serial) communication between master and slave.

    2)Do we need to use any additional filter apart from the isolators.

    3) Have you tested any time before with this same configuration?

    Thanks & Regards,

    Suriyaprakasam

  • 0 in reply to Suriyaprakasam Chinnusamy
    TI__Genius 11480 points
    Hi Suriyaprakasam,

    This set of questions really have no easy answer, unfortunately. IT will largely depend on what your system noise will look like, which i can't predict. You may consider using a shielded cable. Another big factor is how long the cable between the two boards will be. UART is also a single ended communication protocol, so it will be more susceptible to common mode noises. To be honest, i have rarely seen this application put into use. In my experience i have seen either isolated CAN come into the slave board with a local MCU, or an additional pl455 was used as a communication bridge to utilize the differential daisy chain communications.
  • 0 in reply to David Wiest Jr
    Prodigy 100 points
    Hi David,

    Yes, i agree your point. Differential and daisy chain communications are most preferable communications in noise environment but it will add up project cost even though i am thinking to go with can controller in master board and iso can in slave board.

    i could not able to find can controller which supports uart input and provide the CAN output. Could you able to suggest me can controller which supports uart communication.

    Thanks for your support and understanding.

    Regards,
    Suriyaprakasam C
  • 0 in reply to David Wiest Jr
    Prodigy 100 points

    Hi David,

    Thanks for your support.

    As discussed earlier i would prefer to go with Daisy Chain master slave configuration for eliminating external noises. please find the attachment for updated configuration kindly review it once and provide youMaster & slave configuration.pptxr comments.

    i have considered 2 Daisy chain configuration since BQ76PL455A Battery monitoring is limited with 16BMU in Daisy chain application.

  • 0 in reply to Suriyaprakasam Chinnusamy
    TI__Genius 11480 points

    Hi Suriyaprakasam,

    Thanks for the ppt... that seems perfectly valid to me.

    So, you intend on using >16 pl455 modules? If so, then the diagram you gave me is  exactly what you would want. If using  fewer than 16 you can drop down to one "string"

  • 0 in reply to David Wiest Jr
    Prodigy 100 points
    Hi David,
    Thanks for your support.
    Yes. We are planning to use graeter than 16 bmu.

    I will keep you posted for further queries

    Regards,
    Suriyaprakasam C