ADM3061E RO issue

I have problem.

A glitch goes out to a RO terminal at the time of an input HL change.

Can't I have advice?

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  • 0
    •  Analog Employees 
    on Dec 7, 2018 11:58 AM

    Hello,

    Thanks for your query,

    To help me assist you with this, could you provide some more detail on your setup conditions?

    What device is driving the A and B signals? The edges at the transitions look faster than I would expect from the ADM3061E.

    You are operating with a 5V power on the ADM3061E, is that correct? How are the A/B signals terminated? Is the ADM3061E device decoupled correctly, with 100nF between VCC and GND?

    I will attempt to recreate this in our lab.

    Kind Regards.

    Neil

  • Thank you very much for your answer.

    Yes,VCC is 5V,add 0.1μF between VCC and GND.

     A/B signals is terminated 120 Ω .

  • >What device is driving the A and B signals?

    ⇒I use MAX22501

    https://datasheets.maximintegrated.com/en/ds/MAX22500E-MAX22501E.pdf

    Is there limit transitions speed?

    when i add 1nf between A and B, work correct 

  • +1
    •  Analog Employees 
    on Dec 12, 2018 1:24 PM in reply to UBOTI

    Thank you for providing more detail on your setup.

    The 1nF capacitor has the affect of slowing down the rise/fall edges into the optimum region for the ADM3061E, giving correct operation. The ADM3061E is optimized for slew rate limited drivers for operation at up to 500kbps. The MAX22500E is optimized for 100Mbps transmission, and has a very fast driver rise/fall time of 3ns. If you are looking for a RS-485 receiver optimized for high speed inputs, the ADM3065E would be a better option.

    I have no MAX22500E parts available in the lab, but I was able to setup your test with an ADM3065E transmitter, which was similar high speed A/B outputs, like the MAX22500E. The capture below shows a ADM3065E receiver correctly receiving data from a ADM3065E transmitter at 100kbps.  

    ADM3065E transmitter, ADM3065E receiver

    Alternatively you could use replace the MAX22510 transmitter with the ADM3061E. This has a slower rise/fall time of >100ns, which is optimum for the ADM3061E receiver. The plot below shows the ADM3061E receiver functioning correctly with a ADM3061E transmitter, at 100kbps.

    ADM3061E transmitter, ADM3061E receiver

    In both plots the Vcc = 5V, and RT = 120ohms, to match your setup.

    Kind Regards,

    Neil    

Reply
  • +1
    •  Analog Employees 
    on Dec 12, 2018 1:24 PM in reply to UBOTI

    Thank you for providing more detail on your setup.

    The 1nF capacitor has the affect of slowing down the rise/fall edges into the optimum region for the ADM3061E, giving correct operation. The ADM3061E is optimized for slew rate limited drivers for operation at up to 500kbps. The MAX22500E is optimized for 100Mbps transmission, and has a very fast driver rise/fall time of 3ns. If you are looking for a RS-485 receiver optimized for high speed inputs, the ADM3065E would be a better option.

    I have no MAX22500E parts available in the lab, but I was able to setup your test with an ADM3065E transmitter, which was similar high speed A/B outputs, like the MAX22500E. The capture below shows a ADM3065E receiver correctly receiving data from a ADM3065E transmitter at 100kbps.  

    ADM3065E transmitter, ADM3065E receiver

    Alternatively you could use replace the MAX22510 transmitter with the ADM3061E. This has a slower rise/fall time of >100ns, which is optimum for the ADM3061E receiver. The plot below shows the ADM3061E receiver functioning correctly with a ADM3061E transmitter, at 100kbps.

    ADM3061E transmitter, ADM3061E receiver

    In both plots the Vcc = 5V, and RT = 120ohms, to match your setup.

    Kind Regards,

    Neil    

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