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Hello,
I am designing a FX3 board with Spartan 6 FPGA.
My question is: "Do I need 22 Ohm termination resistors on GPIF 2 interface".
I couldn't make a signal integrity simulation since there is no ibis model of the FX3 chip.
The PCB will be very small. FX3 and Spartan 6 will be very close to each other.
Nearly all GPIF pins will be connected to the FPGA.
Regards,
Ersin OEZALP
Solved! Go to Solution.
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Hi,
22-Ω series resistors are recommended to avoid the reflection phenomenon, impedance mismatch on the GPIF lines and also due to PCB stack up. Hence, we recommend using 22-Ω series termination resistors to avoid reflection on these lines.
Best Regards,
AliAsgar
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Hi,
There is an ibis model for the FX3. Maybe you need to raise a support case with Cypress to get it.
Sodafarl
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Hi Ersin,
I have absolutely the same question
Should I put GPIF2 22 ohm termination resistors if source IC and FX3 are close to each other?
FX3 acting as signal/clock receiver.
To be more specific, in my particular case:
- Max sourceIC to FX3 GPIF2 wire length is 28.39mm
- Min sourceIC to FX3 GPIF2 wire length is 18.37mm
- Length mismatch 10.02mm
- Source IC clock frequency 74.25 MHz
- Source IC signal rise / fall time = 1ns
I found some guide from Analog Devices https://www.analog.com/media/cn/training-seminars/tutorials/MT-097.pdf
Acording to this guide termination resistors advised if microstrip length is greather than 2 inches * t(rise or fall), ns
I guess no resistors needed for my case because max wire length without termination resistors is 51mm.
What would the Cypress FX3 engineers advise?
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Hi,
22-Ω series resistors are recommended to avoid the reflection phenomenon, impedance mismatch on the GPIF lines and also due to PCB stack up. Hence, we recommend using 22-Ω series termination resistors to avoid reflection on these lines.
Best Regards,
AliAsgar