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Original question:

TCAN1145-Q1: Interface forum: Disable of PIN WAKE configuration

TCAN1145-Q1: TCAN1145-Q1 WAKE signal pull-up

Sergej Dziuba
Prodigy 50 points
Part Number: TCAN1145-Q1
Other Parts Discussed in Thread: TCAN1145EVM

Hi!

On evaluation board for TCAN1145-Q1 we see pull-up resistor R7 for WAKE signal.

The value of R7 is 3.01k, 0603. It seems strange, because if we power from automotive 24VDC, so we get minimum power on this resistor: (24V)^2 / 3.01k = 0.191W.

Please clarify this question.

Thank you!

  • 0
    TI__Mastermind 26806 points

    Sergej,

    For a 24 V supply you would be correct, this could present a dissipation risk to this resistor. This particular setup you've noted for the TCAN1145EVM isn't necessarily a configuration you'd see in an end application. Rather, it provides the user a quick way to generate a LWU for the transceiver without needing an external source.

    In theory, for a 24 V supply, holding the WAKE button (S2) low would dissipate more than 100 mW across this resistor as you noted.

    In an actual system, usually the input to the WAKE pin is relayed from another source, such as a latch, reed switch, relay, etc.

    Best,

    Danny