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TCAN1145-Q1: Wake pin

Ivy Jin
Expert 4605 points
Part Number: TCAN1145-Q1

Hi team,

1.What is the internal structure of the TCAN1145-Q1‘s WAKE pin(Pin9)? Is there a pull-up or pull-down resistance? If so, what is the resistance value? 

2. Could you please help review the schematic and give some comments? 

3.The datasheet shows that the WAKE pin is recommended to have a 22nF capacitance, what is its purpose? 

Thanks in advance!

Regards,

Ivy

  • 0
    TI__Guru 53575 points

    Hi Ivy,

    1. The WAKE pin for TCAN1145 has an internal pull-down current source as shown in Figure 10-3. The equivalent resistance of this current source can be estimated from the low-level input current specification: 2µA max leakage at 1V applied ~= 500k-ohm. 

    2. The CAN bus portion of the schematic is not included here. Do you have the rest of the schematic sheet here to share so I may review the bus? 

    • If the WAKE pin is unused then I would recommend biasing it to ground potential for best current performance. This will be minimally impact full impactful as the internal bias on this pin is very weak. 
    • All decoupling capacitors included and valued appropriately. Ensure placement close to device pins. 

    3. The typical application case for the wake pin has it used with a pushbutton circuit. Because such fast pull-down sources can cause unwanted transients, a capacitor is recommended to smooth this transition. If the WAKE pin is unused, no capacitor is required on the pin as no transitions are expected on this signal line. 

    Let me know if you have any more questions. 

    Regards, 
    Eric Schott