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UCC23511: Driving MOSFET pair as SSR ; simplifying TIDUC87A?

apullin
Intellectual 575 points
Part Number: UCC23511
Other Parts Discussed in Thread: SN6505B

Can UCC23511 (or similar) be used along with 2 N-MOSFETS to get a simple, isolated SSR replacement?
Assuming that the gate-side supply is provided through other means and is also isolated from the control domain.

I am looking at the TIDUC87A app note for SSR replacements, but the isolated control and gate drive block shown in Fig 11 does have quite a few parts.
In my application, this will be repeated x8, so reducing complexity and part count is of interest (and, hopefully, simplicity of hardware verification), even if it is slightly more expensive.

If this appears in any existing TI reference designs or app notes, please let me know.

  • 0
    TI__Guru**** 189399 points

    Hi, Apullin,

    Yes, you can, the only trick is you need an isolated power supply to drive the UCC23511. Here is an example of one:

    Just drive your two fets source to source and connect the common point from the driver to that note and you will be all set.

    If this answered your question, please press the Green button. If you have further questions, let us know!

  • 0 in reply to Don Dapkus
    Intellectual 575 points

    Great! I can eliminate ~100 parts from the BOM with this.

    One follow-on question: 
    The SLLU282A note you provide uses SN6505B and a transformer for a truly galvanically isolated supply.

    Could an implementation follow TIDUC91, where the isolated-side VCC of the UCC23511 could be "self-powered" from the load domain, especially given that it is already LV AC (HVAC)? (assuming a complete supply there, e.g. rectification, vreg, uv lockout)

    However, I do see the potential advantage of using a single transformer + driver to make an isolated supply that could drive the whole gang of 8 drivers on a single dedicated supply. The hesitance to do that is adding a wound transformer to the board is not easy due to the part height and footprint.

  • 0 in reply to apullin
    TI__Guru**** 189399 points

    Hi, Apullin,

    Let me ask my colleague to comment on TIDUC91 for you.