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UCC27201: What is the lowest supply voltage for reliable operation while driving a half bridge.

Nicholas Layshot4
Prodigy 220 points
Part Number: UCC27201

What is the lowest supply voltage for reliable operation while driving half bridge (FDMD82100 by On Semi-conductor). The datasheet states for the UCC27201 the minimum recommended voltage is 8V but another engineer told me 10V is needed for reliable operation because the UCC27201 is designed to inhibit (Low Voltage Lockout) if the drive voltage is insufficient to fully enhance the FET and generally the LVL is set internally to the driver chip at about 7.5V. So, I'm not understanding why 10V is needed?

Thanks,

Nick

  • 0
    TI__Mastermind 21160 points

    Hello Nicholas,

    Thank you for the interest in the UCC27201 driver, I will help answer your questions as I support this device. This is a good question and basically will be a determination of "safe" operation Vs maybe the optimum drive voltage operation.

    Regarding how the UCC27201 will operate. The driver operation is based on the VDD voltage and the HB-Hs voltage being within the operating range regarding UVLO. There is no mechanism beyond that regarding the specific Vgs drive voltage to the MOSFETs.

    The UCC27201 recommended operating range minimum of 8V is based on the VDD rising UVLO threshold maximum of 7.8V. With most MOSFETs with voltage ratings within the driver voltage rating, 100V Vds or less, the designers often choose to operate at typical VDD levels of 9-10V based on the tradeoff of Rdson at a given Vgs and the gate drive losses, which increase as Vgs increases.

    I see that the FDMD82100 has Rdson parameter ratings with a Vgs of 6V, so the device has guaranteed parameters to operate with Vgs at 6V. The Rdson is higher than with 10V Vgs however.

    In the MOSFET datasheet, Figure 2 shows the normalized Rdson Vs Vgs and drain current. This will be a good reference so you can determine if there is any concern driving with Vgs at 8V with the MOSFET peak current in your application.

    You will have to determine if the slight increase in Rdson is a concern. There is no concern regarding the MOSFET switching operation, as confirmed with the datasheet parameters at Vgs=6V.

    Please confirm if this addresses your concerns by selecting the green button on the thread.

    Regards,

    Richard Herring