• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 423 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS24701: TPS24701 failure under 20A current

Lin Zhao
Intellectual 1230 points
Part Number: TPS24701
Other Parts Discussed in Thread: TPS24700,

Hi,

The load is 12V and when the current go up to around 20A, both TPS24700 and TPS24701 got damaged, schematic is as below:

do you have any suggestion?

  • 0
    TI__Guru 57737 points
    Hi Zhao,

    We need more details to find out the cause of failure. Can you please enter the correct values in all the cells of TPS2470x Design Calculator and send it to us.
    you can download the design calculator here:- www.ti.com/.../toolssoftware

    Does the design have a TVS diode at the input of controller ? In case the Controller turns OFF the FET due to any fault condition, there is a possibility of a Voltage Spike at Vcc due to input inductance. If the spike is higher than 30V the device can get damaged.

    Regards,
    Praveen
  • 0 in reply to Praveen GD
    TI__Guru 57737 points
    Hi Zhao,

    Any update on the above requested data?

    Regards,
    Praveen
  • 0 in reply to Praveen GD
    TI__Intellectual 1230 points

    Hi Praveen,

    I'm checking with ctm, will let you know.

    thank you.

  • 0 in reply to Lin Zhao
    TI__Guru 57737 points

    Hi Zhao,

    The design calculator is not entered correctly. please see below comments.

    1. The SOA current values at Vin max that you entered are wrong. Please see below red line for correct values. 

    2. In your schematic, I see only one FET. In the Calculator you mentioned that you have 2 FET's. How many FET's do you have ?

    3. In the design Calculator, you mentioned the start up load in 0.5 Ohms. With so much load, the system will not start. What is the actual load during start up? We generally recommend to start with no load.

    4. Is your maximum Ambient temperature 25C or higher ?

    Even with considering 25C ambient, 1K Start up Current, 2FET's (but correct SOA parameters) the SOA margin is -217%.  This is not acceptable. The FET's will damage. We generally advice greater than +30% margin.

    Also, during ouput Short Condition, the Source is pulled to GND. Now momentarily, +25V Gate voltage is applied across Vgs by controller. The FET Vgs is rated only for +/-20V. This condition can also damage the FET. 

    looks like there is no TVS clamp at the input. if there is a transient event and the controller turns OFF the FET, there will be high Positive Voltage generated across Vcc pin due to input inductance. Any voltage above 18V at Vcc, Sense can damage the device.

    Please click "This resolved my issue" button if this post answers your question.

    Regards,

    Praveen

    8424.TPS2470x_Design_Calculator_Rev-.xlsx