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Part Number: LM5050-1-Q1
We are evaluating LM5050-Q1 for reverse polarity protection. It is for Auto application with the continuous current up to 40A. The nominal input voltage from the battery is 24V.
Can you help us selecting an appropriate N-Channel MOSFET for this application? I am considering CSD18540Q5B (TI), STH272N6F7-6AG (ST), STH265N6F6-2AG (ST),
Thank you very much and best regards,
I am looking into this and will get back on Monday.
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In reply to Karikalan Selvaraj:
For 24V automotive application, we recommend to use 80V rated MOSFETs along with LM5050 or LM74700.
Note that CSD18540Q5B is not automotive qualified.
Other two ST MOSFETs are only 60V rated.
MOSFET selection and TVS selection for 24V battery protection is discussed in datasheet of LM74700 (page 17 and 18, section 10.1.1.4 and Figure 21.)
Other parameters of MOSFET look fine, except Vds rating of the selected 3 MOSFETs.
In reply to John Pan:
I acknowlege your response and would need more time to get back for the above questions.
Is next week okay with you?
Let us know if you need a speedy response.
Next week is fine. Please take your time.
Power dissipation calculation is based on the RTHJ-PCB of the MOSFETs, for the ST parts you indicated, it is 35C/W when mounted on a 1 sq inch PCB area with 2 ounce copper thickness.
To base the calculation, we need to know the PCB board temperature near DRAIN pad of the MOSFETs.
If the PCB board temperature near the DRAIN pads of the MOSFET is 100C, based on the power dissipation calculation of 4.5W worst case, Junction temperature would rise above 100C PCB temperature by 4.5W * 35C/W = 157.5C, that is TJ will be at 257.5C.
This design will not work unless you increase the number of MOSFETs to dissipate more power or add a heat sink.
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