Chapter 6: I/O Features in the Cyclone III Device Family
Termination Scheme for I/O Standards
6–15
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
and
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
VTT
VTT
External
On-Board
Termination
Transmitter
VTT
Cyclone III Device
Family Series OCT
50
Receiver
VTT
OCT
Transmitter
Receiver
Figure 6–9. Cyclone III Device Family Differential SSTL I/O Standard Termination
Termination
Differential SSTL Class I
Differential SSTL Class II
VTT
50
25
50
VTT
VTT VTT
50
25
50
VTT VTT
50
50
50
50
External
On-Board
Termination
25
50
25
50
Transmitter
Receiver
Transmitter
Receiver
VTT
Cyclone III Device
Family Series OCT
50
VTT
Cyclone III Device
Family Series OCT
25
VTT
VTT
50
VTT
50
50
VTT
50
50
50
50
50
OCT
50
Transmitter
Receiver
Transmitter
50
Receiver
Note to
(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 ]
