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TCAN4551-Q1: wake pin

Chung Mike
Prodigy 30 points
Part Number: TCAN4551-Q1

Tool/software:

Hello Experts,

I would like to implement LWU for TCAN4451-Q1 ，the 4550 EVM schematic is use Rseries=33Kohm/Rbias=3Kohm

can i change Rbias to 30kohm?my Vsup is 20V~30V

Best Regards,
Mike

  • 0
    TI__Guru 51006 points

    Hi Mike,

    Today is a holiday. Please give some time for feedback as we return back to the office tomorrow, thanks. 

    Best Regards,

    Michael. 

  • +1
    TI__Guru 53555 points

    Hi Mike,

    The biasing resistor for the WAKE pin may be increased, but the series resistor value will need to be reevaluated to ensure that this weaker pull-up source can pull the signal high after a low-level input. Because the WAKE pin has an adaptive bias, the internal leakage path will switch to a pull-down when a low-level input is detected. This means the the resulting 60k-ohm path to Vsup (Rseries + Rbias) needs to be strong enough to generate a VIH level and IIH is met. 

    The TCAN1043A has the same adaptive bias feature on the WAKE pin and the datasheet includes more application information in Section 8.4.1.5.2 on how to choose these resistor values. Specifically for the high-level input considerations it defines RBIAS < ((VSUPMAX - VIH) / IIH) - RSERIES. For the specifications of the TCAN4551 this leaves us with RBIAS < ((2V) / 25uA) - 33k-ohms = 47k-ohms. Because the proposed value of 30k-ohms fits this requirement there should be no issue changing this value for RBIAS. 

    Let me know if you have any more questions.  

    Regards, 
    Eric Schott