Chapter 6: I/O Features in the Cyclone III Device Family
6–15
Termination Scheme for I/O Standards
Differential I/O Standard Termination
Differential I/O standards typically require a termination resistor between the two
signals at the receiver. The termination resistor must match the differential load
impedance of the bus (Figure 6–8 and Figure 6–9).
The Cyclone III device family supports differential SSTL-2 and SSTL-18, differential
HSTL-18, HSTL-15, and HSTL-12, PPDS, LVDS, RSDS, mini-LVDS, and
differential LVPECL.
Figure 6–8. Cyclone III Device Family Differential HSTL I/O Standard Termination
Termination
Differential HSTL
V
V
TT
TT
External
On-Board
Termination
Receiver
Transmitter
V
V
TT
TT
Cyclone III Device
Family Series OCT
50
OCT
Transmitter
Receiver
(1)
Figure 6–9. Cyclone III Device Family Differential SSTL I/O Standard Termination
Termination
Differential SSTL Class I
Differential SSTL Class II
V
V
V
V
TT TT
TT TT
V
V
TT
TT
50
25
50
50
50
50
50
50
25
25
50
External
On-Board
Termination
25
50
50
Transmitter
Receiver
Transmitter
Receiver
V
TT
V
V
V
V
V
TT
TT
TT
TT
TT
Cyclone III Device
Family Series OCT
50
Cyclone III Device
Family Series OCT
25
50 50 50 50
50
50
50
50
OCT
50
50
Transmitter
Receiver
Transmitter
Receiver
Note to Figure 6–9:
(1) Only Differential SSTL-2 I/O standard supports Class II output.
July 2012 Altera Corporation
Cyclone III Device Handbook
Volume 1
ALTERA [ ALTERA CORPORATION ]
