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XTR111-2EVM: OUTPUT Mosfet Selection

Electronx Electronx
Intellectual 305 points
Part Number: XTR111-2EVM
Other Parts Discussed in Thread: XTR111

circuit requirements that ı need

VSP:16-40V
input voltage range 0-5V
output current range 0-20mA
Output maximum load resistance: 600ohm

SI3459BDV-T1-GE3

(https://www.digikey.com/en/products/detail/vishay-siliconix/SI3459BDV-T1-GE3/2441601?utm_adgroup=&utm_source=google&utm_medium=cpc&utm_campaign=Pmax%20Shopping_Product&utm_term=&utm_content=&gclid=Cj0KCQjw2cWgBhDYARIsALggUhrfe_l0nwmpZW2hZFQwr2om_a5SN6DvvL8OEhZN-keiILMpPRBZjA0aAg4aEALw_wcB)

I chose this as the output mosfet but I have concerns about thermal and power consumption. Will this mossfet meet my needs?

How can I find the power consumed by this mosfet?

  • 0
    Guru 140200 points

    Hi,

    even with only 20mA the heat dissipation will go up to 40V x 20mA = 0.8W in a short-circuit event, which results in a die temperature of 110K/W x 0.8W = 88K over the ambient temperature. So, with an ambient temperature of 40°C the die will rise up to 128°C which is a bit too high, especially if the cooling situation may be degraded because of an nonideal layout.

    So, if longer lasting short-circuit events have to be withstood, I would go for another MOSFET.

    Kai

  • +1 in reply to kai klaas69
    TI__Guru 54566 points

    Hi,

    I agree with Kai, choose a P-FET transistor in a package and thermal characteristics to support your max power condition without overheating, per the max  supply and max output current requirements in the application.  Examples below:

      

    The XTR111EVM uses a 60V PFET in the SOT-223 package. If you refer to the XTR111 board layout on page 7 of the XTR111EVM User's Guide, the drain of the P-FET (pin2, pin4 heat sink) are connected to an isolated copper Fill on Top and connected to another isolated copper fill on the bottom for heat dissipation.

    Thank you and Regards,

    Luis