ADG3304/8 Input driving requirements

Hi

ADG3304 and ADG3308 is same architecture device, I believe.

I found different description in datasheet.

ADG3304 data sheet requests lower output impedance <=150ohm / 36mA peak current capability for output driver.

ADG3308 data sheet doesn't have this description.

ADG3304/8 can drive about 1mA, I think.

For example .

     Vcc=5V

     Vlow th= 5X0.35= 1.75V

     (5-1.75)/6K= 541uA

     When Input level goes to below 1.75V, then change the output, I think.

1. Does ADG3308 inputs need 36mA peak current capability driver?

2. How come these requirements ,36mA and 150ohm ?

moto

  • Hello - I have forwarded your question to our applications engineer.  He is currently on vacation so his response may be slightly delayed.  I apologize in advance for any inconvenience this may cause.

    Regards,

    Rachel

  • Thank you for your support.

    I wish you a Happy new year!

    moto

  • 0
    •  Analog Employees 
    on Jan 9, 2013 8:55 PM

    Hello Moto,

    To confirm, both "Input Driving Requirements" sections of the ADG3304 and ADG3308 are correct. The ADG3304 section is more specific and calculated using worst case scenario, while the ADG3308 is more general.

    In reality, in the input driving requirements are much less owing to the presence of the one-shots and if the switching speed requirements are low.

    Once the Threshold value is achieved, the one shot will kick in and help pull the voltage up or down as required, reducing the required current driving capability.

    Regards,

    Sean

  • Hi Sean

    Thank you very much for your reply.

    In worst case, the driver, that drives ADG330x,  needs 36mA capability.
    But the requirements are much less, in reality.

    In worst case, For ex, some FPGA's output current ability is under 16mA. Is it enough?

    we need to check the output impedance or other specs?

    Could you tell me, how to select the driver from the spec?

    Regards
    moto

  • 0
    •  Analog Employees 
    on Jan 11, 2013 10:25 PM

    Hello Moto,

    The input drive requirements are better described in the ADG3308 datasheet. The cells are the same for both parts.

    Regards,

    Sean