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AM26C31M: DESIGN HELP

krishnaprasad MB
Prodigy 60 points
Part Number: AM26C31M
Other Parts Discussed in Thread: AM26C32, UCC21755-Q1, SN65C1167E,

pls help me to to finalize  the logic .pls reffer  attached picture.basic our requirement is to avoid noise and
reproduce controller card output 3.3V PWM   at end output side sn65C11 as a single ended PWM pulse.already simulated SN65C11 in am26 MODEL IS NOT AVAILBLE FOR SIMULATION.SO NOT POSSIBLE TO COUPLE THESE 2 IC BACK TO BACK.MY DOUBT IS

This 2 IC IS CAPABLE FOR TO REPRODUCE CONTROLLER CARD OUTPUT 3.3V PWM?

THIS IC IS SUPPORT DUTY RATIO VARING PWM ?

  • 0
    Guru 297210 points

    Any transmitter/receiver that is fast enough will work.

    How many channels and what frequency/PWM accuracy do you need?

  • 0
    TI__Mastermind 48327 points

    Hi Krishna,

    As Clemens mentioned - if the device is fast enough for the PWM signal it should work. There would be pulse skew (so duty cycle distortion is possible) but how much of a concern that is really depends on the frequency and how much deviation from the input can the output have.

    So please if you could confirm:

    1. How many channels you need - the device you chose is 4 channel - is this needed or is at different number?

    2. How fast is the PWM signal ?

    3. How much deviation can the system handle - i.e. is there is pulse skew requirement, amplitude requirement (with load), etc...

    4. Do you have a 5V supply rail available - or is the max rail available 3.3V? 

    This application does seem within the realm of possibilities but I will say that it really depends on the other needs of the system.

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Prodigy 60 points

    Thanks for the info sir.clarification about your questions are

    1.4 channels we are using in am26 and 2 chnels for diff to single ended and other 2 single to diffretial in the case of sn65

    2.50khz maximum

    3.we are sensing voltage in inverter through seies resistor devider ..this DEVIDED voltge is go to UCC21755 GATE DRIVER IC output side .THIS voltage converted to APWM (analog pwm )in input side of gate driver IC .THIS APWM IS DUTY RATIO VARYING SIGNAL .WE NEED TO TAKE THIS APWM TO SINGLE ENDED SIDE OF SN65 IC AND OUTPUT DIFFRENTAL SIGNAL TO AM26C32 (DIFF TO SINGLE ENDED)FINALLY SINGLE ENDED GO ADC THROUGH RC.THIS IS THE DESIGN CONCEPT.BUT THIS WILL WORK?

    4.5V POWER SUPPLY AVILABLE SIR

    pls share your opinion and conclusions about this idea 

  • 0 in reply to krishnaprasad MB
    Guru 297210 points

    This is possible.

    The schematic does not show the termination resistor at the receiver. A resistor that matches the characteristic impedance of the cable/traces is necessary to avoid reflections.

    The UCC21755-Q1's APWM output has a frequency of 400 kHz, which corresponds to 2.5 µs. This means that a skew of 2500 ns would result in an error of 100%, and 25 ns, 1%.

    The skew of the AM26C31M is 0.5 ns typical, 4 ns in the worst case. That of the SN65C1167E's receiver is not specified, but is probably similar. So the total skew is about 1 ns (0.04%) typical, 8 ns (0.32%) worst case.

  • 0 in reply to krishnaprasad MB
    TI__Mastermind 48327 points

    Thank you for the prompt response!

    So what Clemens said is 100% correct - this device will meet all of the needs and is a possible use case - so the AM26C31M will be able to work in these conditions. 

    The one thing to note is that this device has a minimum supply requirement of 4.5V - so if there is any tolerance on your power supply and it dips below 4.5V there could be some unexpected behavior so please keep that in mind if designing with this device; but overall I think this is a possible use case and I don't see too much concern in the proposal.

    Please let me know if you have any further questions!

    Best,

    Parker Dodson