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UCC28711: Reliability and testing

Murali Harikrishnan1
Prodigy 80 points
Part Number: UCC28711
Other Parts Discussed in Thread: UCC28600, , UCC28710

Hi,

We are proposing to use the UCC2871X family of PSR for our sub 70W  power supplies. The input is 3 phase rectified and used in an aircraft. The voltage levels are 100V DC to 600V DC. It is similar to TIDA - 00173.

1. Is this part (family) suitable for High reliability applications.

2. We need to prove correct operation of the controller under all operating conditions and combinations. Considering adherence to the Datasheet parameters can this be established.

3. If 2 above is achievable, do you have any guidelines for testing the application.

4. Would you be willing to share the internal logic design of the controller for us to ascertain we have tested all modes, including transitional ones.

5. What is the max gate capacitance the internal driver can support using Low Vgs FET's.

6. With a Vgs of 14V, is the driver able to support SIC Mosfets.

Regards,

Murali

  • 0
    TI__Guru* 86286 points

    Hello,

    Please see the answers to your questions below.

    1. Is this part (family) suitable for High reliability applications.

    > The UCC2871X has been designed for high reliability applications.  However at 70W the device may hard switch instead of  valley switch.

    > At 70W you could consider using a quasi resonant fly back back converter.  The UCC28600 should be able to work in this application.

    2. We need to prove correct operation of the controller under all operating conditions and combinations. Considering adherence to the Datasheet parameters can this be established.

    > The data sheet lists the test conditions and you should be able to reproduce the results.

    3. If 2 above is achievable, do you have any guidelines for testing the application.

    > The data sheet lists the test conditions and you should be able to reproduce the results.

    4. Would you be willing to share the internal logic design of the controller for us to ascertain we have tested all modes, including transitional ones.

    >This is proprietary information and cannot be shared.

    5. What is the max gate capacitance the internal driver can support using Low Vgs FET's.

    > The UCC28711 was designed to source 25 mA to drive the FET.  Please refer to section 8.2 for a functional diagram.

    > This device has been used with FETs with gate capacitances up to 1 nF.

    > However, based on your application this may vary and it may be more efficient to use an external gate driver.

    >I was going to suggest that you could use the excel design tool to estimate the FETs losses.  However, your design will be hard switched and it will not give a good estimation of the FET losses.  However, you could use to estimate the power dissipation of the IC.   

    >Since this is a 70W application the UCC28600 would be a better choice and has and excel tool to help you with your design.

    6. With a Vgs of 14V, is the driver able to support SIC Mosfets.

    >The UCC28710 does have a DRV clamp of 14V.  The data sheet give a typical of 14V with a maximum of 16V without a minimum.  If we assume for the minimum to be 12V it could drive FETs with a miller plateau of 11V or less.  Most silicon FETs have miller plateau of around 10 V.  One thing to be cautious of is the turn time with the 25 mA drive current this can affect your maximum duty cycle.  It may beneficial to use an eternal FET driver for this application if the turn on times are too long.

    Regards,