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UCC27200: Broken Issue

Part Number: UCC27200
Other Parts Discussed in Thread: LM5025, UCC27201


We are using UCC27200 as active clamp Power supply, LM 5025 together.

We found that this parts has broken when applied 48Vdc power without VDD. This power comes through main transformer primary side.

We believe that voltage ratings is over 120V so our application is quite low. Please reply what is wrong?

In addition with the LM5025 controller, when activated 7.6V typ voltage applied from LM5025 then UCC27200 seems to fail (Broken?).

After reached 8V VDD to UCC27200, it goes up normal operation.

  • Hello,

    With 48V applied on the HV input the driver should be within its ratings if there is no switching. Without information such as schematics and ideally scope waveforms it is difficult to comment what may be the issue you are seeing in your application.

    Can you provide information such as the operating conditions of VDD range and VIN. The normal power sequence of VIN and VDD, which one usually applied first.

    Schematics and scope plots will help to provide more comments on what may be occurring to damage the driver. Do you have any information regarding after the driver is damaged, which function is affected, ex HO output not present, LO and HO, VDD bias short etc.

    Our 100V drivers are used quite often in active clamp topologies so there is not any inherent compatibility issues.


  • Dear Richard

    Thank you for your quick reply.

    Attached is simplified schematics of Active clamp, especially primary side.

    Please refer to Fig 2. 

    Behavior of the UCC27200 when reached broken, VDD to GND is "short condition".


  • Thank you for the basic schematic,

    The information that the failure is from VDD to ground is somewhat helpful. Although it is interesting that just applying the HV input seems to cause some issue.

    To provide some better advice, can your provide the component values on the gate driver IC? VCC capacitance, HB to HS capacitance, external gate resistance, HO and LO.

    If there is a VDD to GND short on the driver IC, can you confirm the VDD voltage waveform on the conditions you describe that can cause some issues? VDD overvoltage can certainly be a cause of driver failure. Also confirm the HO, HB and HS voltage during the same sequence of concern, to confirm there is not some voltage beyond the IC ratings, and some unexpected voltage transient(s).


  • Richard 

    Thanks for your awareness. But now debug and analysis duration so our engineering manager cannot provide real schematics, otherwise he has to spend much time..... Sorry. Well I have to repeat similar questions regarding broken issue.

    1)  Does this device have possibilities to reach broken condition when applied 48V to HS without VDD input?

    2)  During transition of activation, common Power supply with LM5025 will rise up to 7.6V to UCC27200 VDD too, 48Vdc will apply to HS pin in the same time.

        This means, 48V HS input come before VDD become 8V. In this case, does this device have possibilities of damage ?

    I understand you mentioned before that need to clarify more detail conditions such as schematics or waveforms.

    We do not have enough time to analysis only this device and we are going to use external Power supply and considered power up sequence from next design.

    I am waiting forward quick reply.

    regards, Keiichi 


  • Hello Keiichi,

    To answer your questions.

    The driver should not have an issue with 48V applied to HS before the VDD is applied. Maybe you can supply some component values, such as the HS to HB capacitor value, VDD capacitor value, and external resistance from the HO and LO to the MOSFET gate?


  • Dear Richard

    Attached is schematics of the Active Clamp Power Supply using UCC27200(Block A-1) and LM5025(Block A-2).

    You can confirm capacitor and resistor values around gate driver.

    Could you please give your comment against process of broken for the UCC27200.

    regards, Keiichi ACF-PS2_01_sch.pdf  

  • Hello Keiichi,

    Thank you for the schematic information update. I see that the MOSFET for the high side clamp is very low gate charge, so the HB to HS capacitance of 0.22uF on the UCC27200 is more than adequate. I do not see any major concerns on the driver components, I am not however an expert on the LM5025 controller.

    I di have some comments where I have seen start-up sequencing issues before. It is not clear from the biasing of the controller and the bias for the UCC27200 which one will start first and reach the IC UVLO threshold first.

    The VDD for the driver needs to exceed the UCC27200 UVLO threshold before the LM5025 IC starts the start up sequence. This is to make sure that the driver is responding during the time that the controller is going through the soft start sequence. If the driver is delayed on starting, the pulse width may be much higher than the intended soft start beginning pulse widths.

    The UCC27200 is the CMOS version of the UCC2720x drivers. the LI and HI input rising thresholds are as high as 8V with a 12V VDD bias. Make sure that the LM5025 PWM outputs are beyond the UCC27200 input rising thresholds. The UCC27201(A) is a TTL version driver with lower input thresholds if that is required.

    I would confirm the startup sequence details as outlined above.

  • Richard

    Thanks a lot for your answer.

    Yes I know we should provide more detail time domain sequence or waveforms VDD and Vin but unfortunately we have not seen them since we found that a gate-driver broken.

    Therefore I would close this loop, questions and answers. Your comments and answers are enough at this time.

    Well we are going to use external power supply for gate driver, separated with controller's VDD.

    Maybe we do not take care about startup sequence between controller and gate-driver.

    If we have any troubles during designing process, I would like to use this post.   Thank you again,