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ISO7421 performance at low frequecies

Simon Peacock30
Prodigy 70 points
Other Parts Discussed in Thread: ISO7421, ISO7321C

Hi There

I am looking at replacing our H/S optocouples with an ISO7421 as we require a feedback path but require some extra information.

We are using the "opto" to send/receive high precision IRIG-B data  so approximately 1 kHz but the edge location is very important to us.

My Question.. at these lower frequencies, what is the edge distortion like? will the internal OSC and PWM/Filter introduce a significant lag or will the high speed input override this?

Thanks

Simon

  • 0
    TI__Genius 10005 points

    Hi Simon,

    First, I'd like you to also consider our latest dual channel isolator ISO7321C for your application. ISO7321C has integrated input noise filter and excellent EMC performance.

    Regarding your original question, our architecture is inherently low distortion / low jitter and the internal signal propagation is seamless. The end user really only need to look at the propagation delay specification in the data sheet regarding delay from input to output.

  • 0 in reply to Saleem Marwat
    Prodigy 70 points

    Unless there is a compelling reason, the ISO7421/E has far better timing performance with lower delays although no jitter graphs... and is about the same price. 

    Input filter isn't that important since this is a 3.3V dedicated I/O line from a CPU.

    EMC .... We are using the isolation for common mode EMC protection, we also use two MOSFETs as a current amplifier and a TVS for differential protection

    Simon