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How to use the ADuM4138?


        My Client was drived IGBT Module (6MBI150XBA120-50) by ADuM4138. As following is their issue for ADuM4138.

  1. About desaturation detection, how to design & optimize the RBLANK, CBLANK and RDESAT for their IGBT?
  2. About Miller Clamp, how to design the MOFET circuit and select the specification of MOSFET?
  3. When ADuM4138 work with IGBT Module and ambient temperature is 40°C, the package temperature of ADuM4138 was 90°C. Was it normal? If not. What was the cause of temperature rise?

        Also, if you have more information for the above issues (for example: application notes, design guides or journals), please provide it for me. Thank you.


[edited by: Klex Lin at 4:09 PM (GMT 0) on 19 Jan 2020]
  • Hello,

    1) For the desat blanking, Rblank is optional, and allows for more current than the internal current source that is normally present on the Desat pin. The usual design sequence for the desat components is to first choose a target blanking time. For IGBTs, this is often around 2 µs. The higher the blanking time, the more noise robust the system is, but the longer a potential short circuit even can exist. For IGBTs with a 10 µs withstand time, choosing a 2 µs blanking is a good value. Once the blanking time is chosen, we note that the internal DESAT current source is typically 490 µA. Using I=C*dv/dt, the capacitance chosen is around 110 pF. If a larger desat blanking capacitor is desired, increasing Cblank while simultaneously adding current through Rblank can achieve the same timing.

    Rdesat is used to limit current coming from the collector of the IGBT. This value is usually around 200-1kΩ.

    2) For the Miller clamp, low Rdson and small gate charge is generally desired. I personally like the IRLML2030TRPBF MOSFET for the external Miller clamp.

    3) Gate Driver IC self heating is a common occurrence, especially with large loads. The 6MBI150XBA120-50 has an total gate charge of around 1100 nC, which is very large. The power dissipated while switching the IGBT will be approximately:


    For 20 kHz, and 20V, we get around 440 mW. If the external series gate resistors chosen are very small, most of the power dissipation occurs within the gate driver IC. Multiplying this by theta-JA, we can get an estimated rise of 27ºC just from the gate drive switching. Adding the other quiescent losses, the temperature rise the customer is observing is possible. One thing to try is to increase the values of the exgternal series gate resistors on Vout_on and Vout_off.

    What switching frequency and voltage is the system being operated at?


  • Hi ,

    Sorry for the delay but it's Chinese New Year holiday. 

    Your reply is very useful for my client,  He had cleared issue and satisfied with your feedback. Thanks a lot for your support.