Stratix® V Device Handbook: Volume 1: Device Interfaces and Integration

ID 683665
Date 10/18/2023
Public
Document Table of Contents

5.7.1. RS OCT without Calibration in Stratix® V Devices

The Stratix® V devices support RS OCT for single-ended I/O standards. RS OCT without calibration is supported on output only.

Table 43.  Selectable I/O Standards for RS OCT Without CalibrationThis table lists the output termination settings for uncalibrated OCT on different I/O standards.
I/O Standard Uncalibrated OCT (Output)
RS (Ω)
3.3 V LVTTL/3.3 V LVCMOS 25/50
2.5 V LVCMOS 25/50
1.8 V LVCMOS 25/50
1.5 V LVCMOS 25/50
1.2 V LVCMOS 25/50
SSTL-2 Class I 50
SSTL-2 Class II 25
SSTL-18 Class I 50
SSTL-18 Class II 25
SSTL-15 Class I 50
SSTL-15 Class II 25
1.8 V HSTL Class I 50
1.8 V HSTL Class II 25
1.5 V HSTL Class I 50
1.5 V HSTL Class II 25
1.2 V HSTL Class I 50
1.2 V HSTL Class II 25
Differential SSTL-2 Class I 50
Differential SSTL-2 Class II 25
Differential SSTL-18 Class I 50
Differential SSTL-18 Class II 25
Differential SSTL-15 Class I 50
Differential SSTL-15 Class II 25
Differential 1.8 V HSTL Class I 50
Differential 1.8 V HSTL Class II 25
Differential 1.5 V HSTL Class I 50
Differential 1.5 V HSTL Class II 25
Differential 1.2 V HSTL Class I 50
Differential 1.2 V HSTL Class II 25
SSTL-15 25, 34, 40, 50
SSTL-135 34, 40
SSTL-125 34, 40
SSTL-12 40, 60, 240
HSUL-12 34.3, 40, 48, 60, 80

The following list specifies the default settings for RS OCT without calibration in the Intel® Quartus® Prime software:

  • For all non-voltage-referenced, HSTL Class I, and SSTL Class I I/O standards—50 Ω.
  • For HSTL Class II and SSTL Class II I/O standards—25 Ω.

Driver-impedance matching provides the I/O driver with controlled output impedance that closely matches the impedance of the transmission line. As a result, you can significantly reduce signal reflections on PCB traces.

If you select matching impedance, current strength is no longer selectable.

Figure 92. RS OCT Without CalibrationThis figure shows the RS as the intrinsic impedance of the output transistors. Typical RS values are 25 Ω and 50 Ω.


To use OCT for the SSTL Class I I/O standard, you must select the 50 Ω RS OCT setting, thus eliminating the external 25 Ω RS (to match the 50 Ω transmission line). For the SSTL Class II I/O standard, you must select the 25 Ω RS OCT setting (to match the 50 Ω transmission line and the near-end external 50 Ω pull-up to VTT).