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Altera_Forum's avatar
Altera_Forum
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12 years ago

Configuration I/O voltage

I am attempting to locate 2.5V LVDS differential signals into Bank 3A of a Cyclone V device - this being the Bank that also contains the Configuration pins. In Quartus II - Device Assig...
Altera_Forum's avatar
Altera_Forum
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11 years ago

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Did you determine if it is possible to have bank 3A at 2.5V? I am facing the same issue. I want to use AS config mode and also need almost all available LVDS inputs on the device. The documentation indicates that Vccpgm must be at 3.0 or 3.3V for AS mode, but from what I can see makes no mention of bank 3A Vccio requirements. If bank 3A Vccio must be at 3.3V, I cannot place all the LVDS inputs.

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You should take a look at the information on the pins that are powered

up by VccPGM in http://www.altera.com/literature/hb/cyclone-v/cv_52007.pdf page 7. Various of the signal pins power up using VccPGM and then when configured, switch to using VCCIO for the Bank that they are in. You might have to provide some form of isolation for the lower voltage devices when the pins are operating at the higher of vccPGM and VCCIO - but this will not be very neat.
EdJ's avatar
EdJ
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4 years ago

I have this same question now (7 years later). Did it work out for you the way you wanted? (I've seen too many mistakes with configuration circuits to not ask this question.)

I am using LVDS inputs in bank 3A of the Cyclone V E. I want to use the ASx4 configuration scheme (EPCQ128) and be able to program the config device through JTAG using the Serial Flash Loader. It seems straightforward based on the documentation:

VCCPGM
"The configuration input buffers do not have to share power lines with the regular I/O buffers in Cyclone V
devices.
The operating voltage for the configuration input pin is independent of the I/O banks power supply,
VCCIO, during configuration. Therefore, Cyclone V devices do not require configuration voltage
constraints on VCCIO."
We are using VCCPGM = +3.3V which is required for the ASx4 configuration scheme, while VCCIO3A = +2.5V (required by LVDS).
The JTAG power and pull up should be VCCPD3A = VCCIO3A = +2.5V.
Let me know if there is any problems hiding here.
Thanks,
Ed