I have a question,Please tell me about ADuM3160.

(1) PIN terminal
Is it a problem to think of it as a digital input terminal
Is it correct by recognizing that the upstream side is digitally switched in the isolated state with or without pull-up?

(2) Series termination resistance when used at full speed
When using the "PC board layout" of the data sheet at full speed, series terminating resistor 24 Ω ± 1% is required.

Should be placed close to the ADuM3160's terminal and matched to 90Ω ± 15% differential impedance

In CN - 0373, there is a circuit diagram without resistance on the downstream side.
It may be because there is a USB controller the most recently, but please tell me the condition that series terminating resistor is necessary / unnecessary.



Best Regards


  • 0
    •  Analog Employees 
    on Mar 30, 2018 6:39 PM

    Hello HOD,

    1) I am not sure exactly what you mean by the asking if PIN is a digital input.  It is a digital input that takes a logic level signal, It has a couple of functions, first it controls the application of the pull-up on the Upstream side, in addition it will block data transfers while it is deasserted.  For instance you can not simply pull it low and provide your own external pull-up on the upstream side.

    2) The terminations 24.1ohm termination resistors should be as close to the package pins as possible.  The reason they are there is because internal resistors available in the chip are not precise enough to meet the requirements of the USB standard, so we pair a sloppy internal resistor with a precise external resistor to make the proper value and tolerance of the pair.  These values will minimize impedance mismatch and ringing on the cable and board traces.  To make it best, match the trace impedance to the cable impedance.

    3) the external terminations are not required for low speed applications where the internal transceivers are reconfigured to slow the slew rate.  You should use the terminations if you are using full speed.

    I hope this helps,

    Best regards,