3.1. Guideline: VREF Sources and VREF Pins
For Intel® Stratix® 10 devices, consider the following VREF pins guidelines:
- Intel® Stratix® 10 devices support internal and external VREF sources.
- There is an external VREF pin for every I/O bank, providing one external VREF source for all I/Os in the same bank.
- Each I/O lane in the bank also has its own internal VREF generator. You can configure each I/O lane independently to use its internal VREF or the I/O bank's external VREF source. All I/O pins in the same I/O lane use the same VREF source.
- You can use the internal VREF with calibration to support DDR4 using the POD12 I/O standard.
- You can place any combination of input, output, or bidirectional pins near VREF pins. There is no VREF pin placement restriction.
- The VREF pins are dedicated for voltage-referenced single-ended I/O standards. You cannot use the VREF pins as user I/Os.
- Connect unused VREF pins to GND.
For more information about pin capacitance of the VREF pins, refer to the device datasheet.
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