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CSD19534KCS: Heat generation Calculation in MosFET.

Prabhu Selvaraj
Intellectual 305 points
Part Number: CSD19534KCS
Other Parts Discussed in Thread: CSD19536KCS

Hi,

We are building an BMS for our automotive application for which, are in need of Driver MOSFETs to control the charge and discharge path. The requirement of the driver is for 15 A and 42 V. We looking forward to choose this "CSD19534KCS", part in our design for the same purpose. 

How can we calculate the heat generated by the MOSFET when carrying 15 A of current through it (At full load) ?

We are in an Idea of paralleling up the MOSFET to carry the same current and Less heat generation and we want to know how to calculate the heat generation for this MOSFET in order to match the thermal requirements.

If we need to conduct about 100 A current via the power path, is it ok to use 3 × CSD19534KCS MOSFETs ?

Thank you

  • +1
    TI__Mastermind 38410 points

    Hello Prabhu,

    Thanks for your interest in TI FETs. Please note, none of our FETs are automotive qualified and there are no plans to complete auto qualification for any TI discrete/power block MOSFET products. The power dissipation in the charge and discharge FETs is purely I^2 x Ron conduction loss. The CSD19534KCS max on resistance at VGS = 10V is 16.5mΩ. Assuming TJmax = 125°C, the on resistance positive temperature coefficient is about 1.8 (see Figure 8 in the datasheet). The power dissipation for a single FET carrying 15A: Pcond = 15A x 15A x (16.5mΩ x 1.8) = 6.7W. This FET is in a heat-sinkable TO220 package capable of higher power loss with a properly designed heat sink.

    The power dissipation for 3 parallel FETs carrying 100A: Pcond = 100A x 100A x (16.5mΩ x 1.8)/3 = 99W or 33W/FET. Even with a heatsink, I don't think the CSD19534KCS can dissipate this much power. The conduction loss can be reduced by using a FET with lower on resistance such as the CSD19536KCS (2.7mΩ max at VGS = 10V & 4.8W) and/or by paralleling more FETs.

    There is an Excel-based load switch FET selection tool which can be used to estimate power loss for up to 3 different TI FET solutions.

    Best Regards,

    John Wallace

    TI FET Applications