a2f500m3b-1csh484 Actel Corporation, a2f500m3b-1csh484 Datasheet - Page 53

• Manufacturer Part Number: a2f500m3b-1csh484
• Description: Actel
• Manufacturer: Actel Corporation

Figure 2-12 • LVDS Circuit Diagram and Board-Level Implementation
OUTBUF_LVDS
Differential I/O Characteristics
Physical Implementation
Configuration of the I/O modules as a differential pair is handled by Actel Designer software when the
user instantiates a differential I/O macro in the design.
Differential I/Os can also be used in conjunction with the embedded Input Register (InReg), Output
Register (OutReg), Enable Register (EnReg), and Double Data Rate (DDR). However, there is no
support for bidirectional I/Os or tristates with the LVPECL standards.
LVDS
Low-Voltage Differential Signaling (ANSI/TIA/EIA-644) is a high-speed, differential I/O standard. It
requires that one data bit be carried through two signal lines, so two pins are needed. It also requires
external resistor termination.
The full implementation of the LVDS transmitter and receiver is shown in an example in
building blocks of the LVDS transmitter-receiver are one transmitter macro, one receiver macro, three
board resistors at the transmitter end, and one resistor at the receiver end. The values for the three driver
resistors are different from those used in the LVPECL implementation because the output standard
specifications are different.
Along with LVDS I/O, SmartFusion also supports Bus LVDS structure and Multipoint LVDS (M-LVDS)
configuration (up to 40 nodes).
FPGA
P
N
Bourns Part Number: CAT16-LV4F12
165 Ω
165 Ω
140 Ω
R e v i s i o n 3
Z
Z
0
0
= 50 Ω
= 50 Ω
Actel SmartFusion Intelligent Mixed Signal FPGAs
100 Ω
N
P
FPGA
+
–
Figure
INBUF_LVDS
2-12. The
2- 41