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MAX3221: ROUT current, rise, and fall times

Ted Casper
Prodigy 90 points
Part Number: MAX3221

Is there a specification or data available for output current of ROUT?  The data sheet has voltage levels but does not mention output current capabilities.  Also, are there values for rise and fall times of ROUT?

  • 0
    Guru 282390 points

    The specified test conditions are −1 mA and 1.6 mA. (When connected to a CMOS input, the actual output current is near zero.)

    The edge speed depends on the capacitive load; see [FAQ] What is the output transition rate for a logic device?

  • 0
    TI__Mastermind 46857 points

    Hi Ted,

    Clemens is correct - the test conditions are specified for -1mA (1mA leaving ROUT pin at "High" output voltage) and 1.6mA (1.6mA being sunk into the ROUT pin) and in general ROUT is connected to a high impedance pin - so the current test points (-1mA and 1.6mA) can be used to help size biasing resistors (pull down resistors should refer to 1mA value and pull-up resistors should be sized in accordance with the 1.6mA for most in-line answer with datasheet)

    As for transition time - we don't have a direct rating, but the FAQ that Clemens provided is probably the best information we have that will allow you to approximate this value - but as also stated in the FAQ testing in your own specific system setup is going to have the most value - but the approximation steps are listed - and that process is is something we use when we don't have direct data to give. 

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Prodigy 90 points

    Thank you for your insight.  I was looking at what transition times might be worst case (load capacitance adjusted) as to make sure trace lengths wouldn't be a concern.  It would be nice to know the ROUT drive/sink capabilities to develop a simple .ibs model for the ROUT pin.  I'll go measure a device to get typical rise/fall values versus load C but based on the low current pull up or pull down data sheet values doubt there is a concern for an unterminated trace.