DC and Switching Characteristics
LatticeECP/EC Family Data Sheet
Lattice Semiconductor
RSDS
The LatticeECP/EC devices support differential RSDS standard. This standard is emulated using complementary
LVCMOS outputs in conjunction with a parallel resistor across the driver outputs. The RSDS input standard is sup-
ported by the LVDS differential input buffer. The scheme shown in Figure 3-4 is one possible solution for RSDS
standard implementation. Use LVDS25E mode with suggested resistors for RSDS operation. Resistor values in
Figure 3-4 are industry standard values for 1% resistors.
Figure 3-4. RSDS (Reduced Swing Differential Standard)
VCCIO = 2.5V
294
Zo = 100
+
VCCIO = 2.5V
121
100
-
294
On-chip
Off-chip
Emulated
RSDS Buffer
Table 3-4. RSDS DC Conditions
Parameter
Description
Typical
20
Units
ohm
ohm
ohm
ohm
V
Z
Output impedance
OUT
R
R
R
Driver series resistor
Driver parallel resistor
Receiver termination
Output high voltage
Output low voltage
294
S
121
P
100
T
V
V
V
V
1.35
1.15
0.20
1.25
101.5
3.66
OH
OL
OD
CM
BACK
V
Output differential voltage
Output common mode voltage
Back impedance
V
V
Z
ohm
mA
I
DC output current
DC
3-11
LATTICE [ LATTICE SEMICONDUCTOR ]
