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TPS54260: Input protection for load dump and false polarity in 24V system

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Replies: 6

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Part Number: TPS54260

I am planning to use TPS54260 or LM25011 as a step down converter for the system. Input sources are the batteries from cars, trucks etc and output needed is 5V and 2A for the system.

Input should be protected like stated in ISO-7637-2 and ISO-16750-2. What kind of protection circuit i need to build in front of the DCDC?

TI has one application note, SNVA681A, where some protection mechanisms are presented. Can this Load Dump Protection Application Circuit used like presented in Figure 6 also for 24V systems where load dump transients can be as high as 202V?

At least my concern is on Q1 (SFT1342) if V(DSS) = -60V of this FET is enough for this 202V transient? Is there something else I should pay attention.

6 Replies

  • Please refer to TI design www.ti.com/.../TIDA-00699 for indepth details of automotive front end protection design .

    --Ambreesh
  • In reply to Ambreesh Tripathi:

    Now basically there are three main issues in the automotive front end design :

    1. Positive and negative pulses as mentioned in ISO7637 -2 which deals with Electrical transient conduction along supply lines only. These pulses can be of +/-100V and can last for few mS . These positive Negative pulses are dealt with (clamped) TVSs at the front end . So now what you see after TVSs will be clamped positive and negative voltage .

    2. The reverse polarity protection as mentioned in ISO16750 is dealt with diode or PFET or NFET with a driver . Consider using Smart diode from TI product family .

    3. Load Dump as well as jump start : Use Wide input voltage DC/DC converter (36V ) . This will also help in reducing stress on input TVS.

    All the details about how to chose these parts can be found here www.ti.com/.../TIDA-00699 .

    Ambreesh
  • In reply to Ambreesh Tripathi:

    Thank you -

    Can I really use these smart diode controllers with 24V automotive environments? Negative abs max -45V comes limiting factor if I want to use TVS - break at about 32V?
  • In reply to user4052185:

    I wont recommend existing smart diode controller for that application . A -65V Reverse voltage rating smart diode Controller is on roadmap which can satisfy the need .

    ---Ambreesh
  • In reply to Ambreesh Tripathi:

    In case of 24V, i have not found TVS components that could fullfill the requirements for Pulse 5a and Pulse 5b of ISO-7637-2. That is why I am asking help on your reference design on load disconnect model.

    Do you have some more tips on 24V system and 202V load dump protection.

  • In reply to user4052185:

    Hi Dan ,

    I beleive you could do it with two stage TVS solution . Just a thought for your design :

    ---Ambreesh

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