a2f500m3b-1csh484 Actel Corporation, a2f500m3b-1csh484 Datasheet - Page 55

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

Figure 2-13 • B-LVDS/M-LVDS Multipoint Application Using LVDS I/O Buffers
R
T
Z
Z
Z
0
0
stub
Receiver
+
R
R
S
B-LVDS/M-LVDS
Bus LVDS (B-LVDS) and Multipoint LVDS (M-LVDS) specifications extend the existing LVDS standard to
high-performance multipoint bus applications. Multidrop and multipoint bus configurations may contain
any combination of drivers, receivers, and transceivers. Actel LVDS drivers provide the higher drive
current required by B-LVDS and M-LVDS to accommodate the loading. The drivers require series
terminations for better signal quality and to control voltage swing. Termination is also required at both
ends of the bus since the driver can be located anywhere on the bus. These configurations can be
implemented using the TRIBUF_LVDS and BIBUF_LVDS macros along with appropriate terminations.
Multipoint designs using Actel LVDS macros can achieve up to 200 MHz with a maximum of 20 loads. A
sample application is given in
section in
Example: For a bus consisting of 20 equidistant loads, the following terminations provide the required
differential voltage, in worst-case commercial operating conditions, at the farthest receiver: R
and R
-
EN
R
Z
S
stub
T
= 70 Ω, given Z
Z
Z
Table
Z
0
0
stub
Transceiver
+
2-64.
R
T
S
-
EN
R
Z
S
stub
0
= 50 Ω (2") and Z
Z
Z
Z
0
0
Figure
stub
Driver
+
R
D
S
2-13. The input and output buffer delays are available in the LVDS
-
EN
R
Z
S
stub
stub
R e v i s i o n 3
= 50 Ω (~1.5").
Z
Z
Z
0
0
stub
Receiver
+
R
R
S
-
EN
Actel SmartFusion Intelligent Mixed Signal FPGAs
R
Z
S
stub
...
Z
Z
0
0
Transceiver
+
R
T
S
-
EN
R
S
BIBUF_LVDS
Z
Z
0
0
S
= 60 Ω
2- 43
R
T