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LM74502-Q1: 160V Load Dump Protection Application

Part Number: LM74502-Q1
Other Parts Discussed in Thread: LM7480-Q1, LM74502


I designed this circuit to protect the SMPS from 160V load dump. The circuit is attached.

1-Is this circuit suitable for 160V load dump protection? (VOUT clamping)

2-Is %5 Tolerance 56V zener okay for protecting the VS and EN/UVLO pins?

3-Is selected TVS (160V) okay for the desired application?

Best regards.

  • Hi Egemen,

    If there is no possibility of input voltage going negative as low as -200V, you would not need a 200V rated Schottky diode. You can choose the Schottky diode rated appropriately for the maximum reverse voltage that can be applied at the input.

    Also, what is the purpose of the TVS at the input ? The 200V rated FET along with the OV clamp protection of the LM74502-Q1 can protect both the controller and downstream load from input 160V transient. 

  • Hi,

    As you mentioned in a previous thread, in LM7480-Q1 datasheet section 10.3

    I selected the TVS according to Input TVS Selection part of the datasheet.

  • Hi Egemen,

    In LM7480-Q1 example the TVS at the input is required because the LM7480-Q1 IC is rated only for -65V at the input and you will need a TVS to clamp the input voltage during ISO PUlse-1 to within -65V for the IC to withstand and block input reverse polarity. 

    But in this case you are using a Schottky diode at the input which will block input reverse polarity from being seen by the LM74502 device. Hence the TVS at the input is not required.