LFEC10E-3F256C Lattice Semiconductor Corp., LFEC10E-3F256C Datasheet - Page 50

• Manufacturer Part Number: LFEC10E-3F256C
• Description: Latticeecp/ec Family of Fpga Devices Has Been Optimized to Deliver Mainstream Fpga Features at Low Cost.for Maximum Performance And Value, The Latticeecp (EConomy Plus) Fpga Concept Combines an Efficient Fpgafabric With High-speed Dedicated Functions
• Manufacturer: Lattice Semiconductor Corp.

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 scheme shown in Figure 3-3
is one possible solution for RSDS standard implementation. Use LVDS25E mode with suggested resistors for
RSDS operation. Resistor values in Figure 3-3 are industry standard values for 1% resistors.
Figure 3-3. RSDS (Reduced Swing Differential Standard)
Table 3-3. RSDS DC Conditions
5V Tolerant Input Buffer
The input buffers of the LatticeECP/EC family of devices can support 5V signals by using a PCI Clamp and an
external series resistor as shown in Figure 3-4. A suitable resistor can be selected by using the PCI Clamp Charac-
teristic as shown in Figure 3-5.
Figure 3-4. 5 V Tolerant Input Buffer
VCCIO = 2.5V
VCCIO = 2.5V
RSDS Buffer
Emulated
Z
R
R
R
V
V
V
V
Z
I
On-chip
DC
OUT
OH
OL
OD
BACK
S
P
T
CM
Parameter
5V Signals from
Legacy Systems
Output impedance
Driver series resistor
Driver parallel resistor
Receiver termination
Output high voltage
Output low voltage
Output differential voltage
Output common mode voltage
Back impedance
DC output current
294
294
Description
121
External
Resistor
3-8
Zo = 100
DC and Switching Characteristics
Typical
LatticeECP/EC Family Data Sheet
Off-chip
3.3V
Units
100
ohm
ohm
ohm
ohm
ohm
mA
V
V
V
V
+
-