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CSD19502Q5B: Maximum current through body diode

JIJESH P
Prodigy 120 points
Part Number: CSD19502Q5B

Hi Team,

In one of our designs, we use a MOSFET CD19502Q5B. We couldn't find any information about the maximum current of the body diode in the datasheet. It would be extremely helpful if you could share the necessary information.

  • 0
    TI__Mastermind 35150 points

    Hello JIJESH,

    Thanks for your interest in TI FETs. In theory, the body diode current rating is the same as the FET. However, the maximum power loss limitation is the same whether the current flows thru the channel when the FET is on or thru the body diode in the reverse direction when the FET is off. The maximum current and power ratings in the MOSFET datasheet are calculate values as explained in the blog at the link below. To calculate the maximum current thru the body diode, you can equate the conduction loss I² x RDS(on) = I x VSD. For example, the max power dissipation in the datasheet at TA = 25°C is calculated as follows:

    PDmax = (TJmax - TA)/RθJA = (150°C - 25°C)/40°C/W = 3.125W and IDmax = √(PDmax/RDS(on)max) = √3.125W/7.9mΩ (at TJ = 150°C & VGS = 10V) = 19.9A (the datasheet spec is 17A which may be a typo).

    And ISDmax = PDmax/VSD = 3.125W/0.66V (at TC = 125°C & ISD = 19A) = 4.7A

    https://e2e.ti.com/blogs_/b/powerhouse/posts/understanding-mosfet-data-sheets-part-3

    This should be derated if your ambient temperature is higher than 25°C and may increase if RθJA is reduced. Please let me know if you have any questions.

    Best Regards,

    John Wallace

    TI FET Applications

  • 0 in reply to John Wallace1
    Prodigy 120 points

    Hi John,

    Thanks for the response.

    And ISDmax = PDmax/VSD = 3.125W/0.66V (at TC = 125°C & ISD = 19A) = 4.7A

    Couldn't get the point how the ISD=19A  comes in the bracket. Could you please help on this

  • 0 in reply to JIJESH P
    TI__Mastermind 35150 points

    Hi JIJESH,

    Please refer to Figure 9 on page 6 of the datasheet. This is a plot of ISD vs. VSD I pulled up the characterization data collected during product development used to generate these plots to get a better estimate of the body diode forward voltage at the specific current. Please let me know if you have any additional questions.

    Best Regards,

    John

  • 0 in reply to John Wallace1
    Prodigy 120 points

    Hi John,

    Got it. Thank you for your prompt assistance.