Hello,
I selected LM74700-Q1 in my motor controller design. I have a few questions and would like to ask your advice for TVS selection.
Question 1: Could any of SMBJ45A/48A/51A/54A be used for TVS+ and any of SMBJ33A/36A be used for TVS-? In LM74700-Q1 datasheet page 18, it says that for 24V battery system, the minimum breakdown voltage for TVS+ is 48V and the maximum breakdown for TVS+ is 65V. The minimum breakdown voltage for TVS- is -32V and the maximum breakdown voltage for TVS- is 43V. I believe that SMBJ45A, SMBJ48A, SMBJ51A, and SMBJ54A all meet the requirement for TVS+ in addition to the recommended SMBJ58A. And SMBJ30A, SMBJ33A, and SMBJ36A all meet the requirement for TVS- in addition to the recommended SMBJ26A.
Question 2: How does the peak pulse power, P_PPM affect the TVS selection? Since SMBJ has a maximum peak pulse power of 600W at 10/1000 us at 25C, which indicates has less than 150W at 100C. ISO7637-2 and ISO16750-2 requires td at 10 ms. At td of 10 ms, SMBJ only has less than 10% of P_PPM, which leads to less than 60W. I am wondering whether SMBJ is acceptable for a 24V motor control with a typical current of 20A or 30A? What are criteria for selecting P_PPM?
Question 3: Does TVS selection related to the power of the motor, for example 600W (24V and 25A current)? If not, could use the same TVS for 100W, 300W, or 600W BLDC motor drive?
Question 4: Does the recommended SMBJ58A and SMBT26A are only for ESD protection or both ESD and EOS (ISO-7637-2 load dump)?
Sorry for so many questions.
Thanks and I look forward to hearing from you,
John
