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TAS6684-Q1: Diodes on the output

Jiahao Yu
Expert 5180 points

Part Number: TAS6684-Q1
Other Parts Discussed in Thread: TAS6584-Q1,

Hi team,

Wanted to confirm 

  1. whether BD modulation requires addtional diodes on the TAS6684 output, while 1SPW and hybrid don't require that?
  2. what's the reason of it? 

Thanks,

Jiahao

  • 0
    TI__Guru 61670 points

    Hi Jiahao

    PBTL need it, just BD usually needn't.

    Is there any background of this question?

  • 0 in reply to Shadow He
    TI__Expert 5180 points

    Hi Shadow,

    Customer is Li-auto, and previously they use TAS6584-Q1, and then they upgrade to TAS6684-Q1.

    The answer to TAS6584-Q1 is PBTL and high-voltage BD need diodes to GND and battery. 1SPW and hybrid mode don't need it. 

    Just want to make sure TAS6684 and TAS6584 should be the same since no change on the output mode, is this correct?

    Best,

    Jiahao

  • 0 in reply to Jiahao Yu
    TI__Expert 4220 points

    Hi Jiahao,

    See below screenshot from datasheet. 

     

    I'm pretty sure it is the requirement for any output switching mode, but I'll double check with the team and let you know.

    But TAS6684 and TAS6584 should be the same in terms of needing schottky diodes.

    Elise

  • 0 in reply to Elise Xu
    TI__Expert 5180 points

    Hi Elise,

    Thanks for your reply.

    Elise Xu said:
    I'm pretty sure it is the requirement for any output switching mode, but I'll double check with the team and let you know.

    Did you mean this schottky diode is also needed for 1SPW and hybrid mode?

    May I ask what's the reason of adding this schottky diode?

    Best,

    Jiahao

  • +1 in reply to Jiahao Yu
    TI__Expert 4220 points

    Hi Jiahao,

    Jiahao Yu said:
    Did you mean this schottky diode is also needed for 1SPW and hybrid mode?

    Yes, as long as PBTL meets either of the above conditions in the screenshot (PVDD>14.4, or Fsw>480kHz), we recommend using the diodes.

    May I ask what source you got the idea that it's not necessary for 1SPW and hybrid?

    Jiahao Yu said:
    May I ask what's the reason of adding this schottky diode?

    The diodes are to reduce ground bounce. It allows the extra stored energy in the LC to dissipate thru the external diodes (it's an extra current path) faster than it can thru the internal body diodes of the output mosfets. 

    Elise

  • 0 in reply to Elise Xu
    TI__Expert 5180 points

    Hi Elise,

    Thanks for explaining!

    Elise Xu said:
    May I ask what source you got the idea that it's not necessary for 1SPW and hybrid?

    I got this answer from China apps team, but I cannot find the email thread since it needs to trace back to May. 24..

    Elise Xu said:
    Yes, as long as PBTL meets either of the above conditions in the screenshot (PVDD>14.4, or Fsw>480kHz), we recommend using the diodes.

    I will take this as the answer. 

    Best,

    Jiahao