- #1
Jdo300
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Hello All,
I have two PCBs, board A and board B. Board A has a 50MHz Crystal that I am making available through a high speed digital isolator (IL711-2E) to a chip that is on board B.
Here's the datasheet on the isolator IC http://www.nve.com/Downloads/il711-2.pdf".
Now, I was thinking about using an SMA cable to go between the boards but given the high frequency, I'm thinking that it might be a good idea to treat the cable like a transmission line and properly terminate the ends. But I don't know much about matching the ends.
I know that my isolator IC can source a maximum of 10mA at 5V and that the other end of the line will goto a CMOS digital input on the destination board.
I spoke to a friend about this and he said that I should put a capacitor and termination resistor in parallel to ground with the CMOS input on board B, and that I should put a resistor in series with the isolator on the board A side. But I'm not sure what values to use for the resistor. Just from looking at the specs for the output drive of the isolator, it can source 10 mA @ 5V so should I assume that it's output impedance is 500 Ohms? If so, then should I use 500 Ohm resistors for the beginning and end resistors mentioned above?
Any help greatly appreciated.
Thanks,
Jason O
P.S. Forgot to mention but I don't expect the cable to be any longer than 6 feet.
I have two PCBs, board A and board B. Board A has a 50MHz Crystal that I am making available through a high speed digital isolator (IL711-2E) to a chip that is on board B.
Here's the datasheet on the isolator IC http://www.nve.com/Downloads/il711-2.pdf".
Now, I was thinking about using an SMA cable to go between the boards but given the high frequency, I'm thinking that it might be a good idea to treat the cable like a transmission line and properly terminate the ends. But I don't know much about matching the ends.
I know that my isolator IC can source a maximum of 10mA at 5V and that the other end of the line will goto a CMOS digital input on the destination board.
I spoke to a friend about this and he said that I should put a capacitor and termination resistor in parallel to ground with the CMOS input on board B, and that I should put a resistor in series with the isolator on the board A side. But I'm not sure what values to use for the resistor. Just from looking at the specs for the output drive of the isolator, it can source 10 mA @ 5V so should I assume that it's output impedance is 500 Ohms? If so, then should I use 500 Ohm resistors for the beginning and end resistors mentioned above?
Any help greatly appreciated.
Thanks,
Jason O
P.S. Forgot to mention but I don't expect the cable to be any longer than 6 feet.
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