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SN65DSI83-Q1: Question about EN

Austin Do
Expert 4205 points

Part Number: SN65DSI83-Q1

Hello team,

I have some questions about using external cap controlled EN in Figure 7. 

  1. It looks capacitance depends on slew rate of VCC supply. How to estimate the capacitance?
  2. How to do 8.3.5 Initialization sequence or reset?

image.png

Best Regards,

Austin

  • 0
    TI__Mastermind 31590 points

    Hi Austin,

    Austin Do said:
    It looks capacitance depends on slew rate of VCC supply. How to estimate the capacitance?

    You could test initially with the 200 nF capacitor as suggested and check whether EN is high 10 ms after Vcc power supply is high. You could use a larger capacitor to increase the rise time, and increasing the delay.

    You could also use a voltage supervisor device to ensure the power-up sequence is followed and that EN is set after Vcc power supply is high and stable.
     

    Austin Do said:
    How to do 8.3.5 Initialization sequence or reset?

    For resetting the device, you could initialize it fully again, by powering down Vcc. Or you could use the controller and use a GPIO pin to control EN so that you can set it high/low and toggle it for reset when required. Using the controller GPIO would be a recommended solution so that you have greater control for the EN pin.

    Best regards,
    Ikram

  • 0 in reply to Ikram Haque
    TI__Expert 4205 points

    Hi Ikram,

    If the customer use external cap only at EN pin, they need to find the appropriate capacitance based on VCC ramp up timing. 

    Then, by adjusting capacitance, need to ensure 10ms before EN pin goes to HIGH. Is my understanding correct?

    Also, hardware reset is not possible if VCC presents. Is this correct?

    Best Regards,

    Austin

  • +1 in reply to Austin Do
    TI__Mastermind 31590 points

    Hi Austin,

    Austin Do said:

    If the customer use external cap only at EN pin, they need to find the appropriate capacitance based on VCC ramp up timing. 

    Then, by adjusting capacitance, need to ensure 10ms before EN pin goes to HIGH. Is my understanding correct?

    Yes this is correct. 

    Are the customer not able to use a GPIO pin to control the EN pin? Since this device needs to be programmed via I2C, they could also connect a GPIO to the EN pin. Can the customer use a GPIO here?

    Best regards,
    Ikram

  • 0 in reply to Ikram Haque
    TI__Expert 4205 points

    Hi Ikram,

    Thanks for clarification.

    Let me discuss with the customer and get back to you again if they have more questions. I will push them to use GPIO.

    Best Regards,

    Austin