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TIDM-02002: PMP21553 + PMP21561 connections + documentation

Part Number: TIDM-02002
Other Parts Discussed in Thread: UCC21530, PMP21553, , PMP21495, PMP21561, ISO7820, PMP21999

Hello!

I have been trying to pitch UCC21530 as an isolated gate driver in an HEV/EV application and have run into some confusion in the documentation. I have a few questions:

  • PMP21495 SCHEMATIC, second pic, shows UCC21530 driving the primary FETs but the block diagram of the PMP21495 User's Guide shows PMP21553 driving the secondary FETs, first pic. The TIDM-02002 guide also confirms that PWM1B/1A are for the primary FETs. Which is correct? Should PMP21553 be driving the primary or secondary FETs?
  • If it is the case that PMP21553 is driving the primary side FETs then why was an isolated gate driver chosen? It seems like the MCU is connected to PGND along with the primary FETs and "primary" side of the UCC21530 isolated gate driver
    • This was why it kind of made sense to me that PMP21553 was used to drive the secondary FETs (really i think it could drive either primary or secondary but the input signals from C2000 have to be one way or the other for control and the connector pinouts of PMP21561 and PMP21553 are unique)
  • PMP21495 + PMP21561 seems redundant a little bit. The signals from C2000 are isolated from the isolated gate driver with ISO7820 and then the ioslated PWM signal is isolated from the FETs with UCC21530 on PMP21561. Realistically wouldnt you only need one or the other of the isolated gate driver or digital isolator?
  • Final thought - i think really either PMP21561 or PMP21553 could be used to drive either primary or secondary side FETs just was hoping to understand the thought process on some of these questions I had. Perhaps it was just to show multiple ways to do isolation or something like that.
  • Kevin,

    Take a look at https://www.ti.com/tool/PMP21999 This is an update to this design. I do believe the documentation needs a few updates, but PMP21999 shows the latest connections.

    You are correct there was redundant isolation, That should have been removed in the new PMP21999 design. Either way was acceptable and eventually one was chosen, I don't believe there was an advantage to one isolation method or the other.

    Regards,
    Cody