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TCAN1145-Q1: About VSUP Connection

Andy Way
Prodigy 55 points
Part Number: TCAN1145-Q1

Hi Experts,

I am considering using a series resistor 4.7K and a 38V clamped TVS to protect TCAN1145-Q1 VBAT pin in 24V truck load dump situation.

But in NXP's TJA1145 Application Hints, I have found that the VBAT pin should not be connected a series resistor to VBAT,

because TJA1145 will consume some extra current when powered up and a signficant voltage drop will be produced across the 

external series resistor.

So I am wondering whether TCAN1145-Q1 has  this similar use situation? 

And second, are there any other methods to protect TCAN1145-Q1 VBAT pin in 24V truck load dump situation?

  • 0
    TI__Guru 74252 points

    Andy,

    TCAN1145-Q1 would be similar in that at worst in normal mode, the VSUP pin consumes 1.5mA. So with a 4.7k series resistor that's a 7.05V drop, which is significant depending on the nominal VSUP voltage in your system.

    As it is, the TCAN1145-Q1 VSUP pin is rated to survive a 12V load dump. A TVS, or something like PTC fuse is a good start for protection during load dump. Your method now is a good start, but you'd have to size the resistor so it would limit the overall power delivered during load dump while still not dropping too much voltage to cause an undervoltage event on VSUP. 

    Regards,

    Eric Hackett