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BQ76PL455A-Q1: bq76PL455A-Q1

elham mirzaei
Prodigy 190 points
Part Number: BQ76PL455A-Q1

Hello I am working with a BMS design Project using bq76PL455A-Q1 ,I just want to initialize the registers of bq76PL455A-Q1 device as a first step of my hardware test .I just make a small PCB board test for it by adding other components on the bread board just to get access to the IC and make sure how it works with the main Processor.

1.I don't know if I have to connect the UART interface to my main Micro controller or I can use the bq76PL455A-Q1  GUI by just using an RS232 to USB converter to my PC?

2.Shall I connect all the Sense pins or I can just get access to the registers without reading any voltages?

3.By using an external power using your reference design,I have to use 12 V with my signal generator?

Thank you in advance

  • 0
    TI__Genius 11480 points
    Hi Elham,

    You are indeed able to use the gui. We recommend a 5V FTDI cable, like this one: www.sparkfun.com/.../9718

    In an application, you would use the MCU UART (TX/RX) to connect to the pl455 RX/TX, and two GPIOs for wakeup and NFAULT.

    You have to be connected to cells or some other source to power the IC and communicate. I recommend reading through the documentation on this page: www.ti.com/.../technicaldocuments
  • 0 in reply to David Wiest Jr
    Prodigy 190 points

    Hi Dave,

    As I understood ,I have to use the serial to USB converter to get access to the registers?but when I want to read and transmit data ,the host is MCU instead of the PC?I mean GUI is just usable by PC?

  • 0 in reply to elham mirzaei
    TI__Genius 11480 points

    Hi Elham,

    It  is really an "either or" situation. The GUI/FTDI cable  is really for evaluation of the IC. If this  is not a commercial project, it may also be useful for demo purposes as well.

    In a true application, such as  a battery monitoring  module  inside an electric vehicle or  renewable  energy storage, Firmware will be loaded to a MCU, and  that will  communicate  to either the  bottom device, or to all  devices (we call this a Multi-Drop configuration), through UART. Many MCU's have a UART  peripheral that can communicate  to the pl455. No USB cable is needed, as there is usually some  wiring  harness or they are on the  same PCB.

  • 0 in reply to David Wiest Jr
    Prodigy 190 points

    Thank you very much Dave.

  • 0 in reply to David Wiest Jr
    Prodigy 190 points

    Hi David,

    My board UART is working with 3.3 V so I have to use a voltage divider ,as I understood the 

    BQ76PL455A-Q1 Uart is working with 5V?

  • 0 in reply to elham mirzaei
    TI__Genius 11480 points
    Hi Elham,

    The MCU uart and pl455 VIO (TX and RX are pulled up to VIO) should be at the same voltage level. If using an opto-isolator, this isn't needed.

    The pl455 UART is compatible with 5V.
  • 0 in reply to David Wiest Jr
    Prodigy 190 points
    Hi Dave, I don't use the opto-isolater and I know my MCU UART IS working with 3.3v.Do you mean that I can not use this MCU ,cause you said they should be at the same level .I I thought I could use a resistor to reduce the voltage and it will not affect the the data.So,what can I do not to change the MCU? Thank you in Advance
  • 0 in reply to elham mirzaei
    TI__Genius 11480 points
    Elham,

    If you do not care about isolation, VIO could be powered from the same supply as the MCU voltage, as is mentioned in the datasheet. if you aren't comfortable with that, you could use a level shifter to go between the 3.3V/5V levels.

    I would stay away from using a resistor divider - the output voltage is going to be dependent on the load current. In general, if you want to step a voltage down + draw any reasonable amount of current, you should use an LDO or switching regulator.
  • 0 in reply to David Wiest Jr
    Prodigy 190 points

    Hi Dave,

    Thank you for all your good information,so I can connect mu vcc from MCU with 5V to the VIO pin and not considering the difference between voltage level?I man it will not affect my data transferring?

    I have another doubt about the clamp TVS diode,

    In my project I am trying to monitor an 8 cells pack Lithium-Ion battery  with 26V ,so the clamp voltage still should be 88V as described in the Datasheet?Or I must select a TV diode with 26V clamp voltage?

    Thank you in advance.

  • 0 in reply to elham mirzaei
    TI__Genius 11480 points

    Hi Elham,

    If you  look at the documentation, VIO can be powered externally (with the MCU supply). This keeps the logic  levels the same from transmitter to receiver.

    I would recommend keeping it  as 88V - this  is  dictated by the absolute max voltage  for the part rather than cell  count. It is chosen to prevent overshoots, transients, etc, from damaging  the part