+ Post New Thread
Results 1 to 5 of 5
  1. #1
    Member level 5
    Points: 1,051, Level: 7

    Join Date
    Oct 2015
    Posts
    85
    Helped
    0 / 0
    Points
    1,051
    Level
    7

    LTC 4367 Transistor burning Issues

    Hi all.
    I'm using LTC4367 for reverse polarity, OV and UV protection. I'm using the FDMD84100 Dual N channel Mosfets and the input voltage is 50V. However, when connected without any load, the output voltage is all OK at the beginning but then it gradually decreases towards zero. Also my transistors have been burnt in most cases and I've tried changing the IC and the transistors countless times. My output current requirement is 7A. OV is 58V and UV is 5V. I've used the resistors according to these values. Also, I've tested both in open load and also by attaching the load, the result is the same.

    I'm attaching my schematic.Click image for larger version. 

Name:	Schematic.png 
Views:	10 
Size:	38.2 KB 
ID:	155089

    Kindly help as I'm stuck at this stage for a very long time now. Thankyou!

    •   AltAdvertisement

        
       

  2. #2
    Super Moderator
    Points: 80,963, Level: 69
    Achievements:
    7 years registered
    Awards:
    2nd Helpful Member
    betwixt's Avatar
    Join Date
    Jul 2009
    Location
    Aberdyfi, West Wales, UK
    Posts
    13,271
    Helped
    4433 / 4433
    Points
    80,963
    Level
    69

    Re: LTC 4367 Transistor burning Issues

    I presume the source connection on Q2 is connected to +50V, it isn't shown in the schematic.
    Gradual reduction in output suggests something is overheating. You are running the device at it's maximum rating, is it adequately heatsinked?

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



    •   AltAdvertisement

        
       

  3. #3
    Member level 5
    Points: 1,051, Level: 7

    Join Date
    Oct 2015
    Posts
    85
    Helped
    0 / 0
    Points
    1,051
    Level
    7

    Re: LTC 4367 Transistor burning Issues

    Quote Originally Posted by betwixt View Post
    I presume the source connection on Q2 is connected to +50V, it isn't shown in the schematic.
    Gradual reduction in output suggests something is overheating. You are running the device at it's maximum rating, is it adequately heatsinked?

    Brian.
    Source connection is left open as this transistor is connected in a back to back common source configuration as shown below.Click image for larger version. 

Name:	sch.png 
Views:	2 
Size:	29.2 KB 
ID:	155093
    Also whose maximum rating are you talking about? The transistors? I am testing my setup in Airconditioned environment with fast speed fan.



    •   AltAdvertisement

        
       

  4. #4
    Super Moderator
    Points: 80,963, Level: 69
    Achievements:
    7 years registered
    Awards:
    2nd Helpful Member
    betwixt's Avatar
    Join Date
    Jul 2009
    Location
    Aberdyfi, West Wales, UK
    Posts
    13,271
    Helped
    4433 / 4433
    Points
    80,963
    Level
    69

    Re: LTC 4367 Transistor burning Issues

    Apologies, your original schematic shows an unconnected source at pin 9 but I see from the data sheet it is an 8-pin device with internally connected source pins.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



  5. #5
    Member level 5
    Points: 1,051, Level: 7

    Join Date
    Oct 2015
    Posts
    85
    Helped
    0 / 0
    Points
    1,051
    Level
    7

    Re: LTC 4367 Transistor burning Issues

    Yes exactly. Thats why i left the source pins open.
    Now coming back to the issue, any suggestions?



--[[ ]]--