
Detailed Specifications
2- 52
R e v i sio n 1 8
LVPECL
Low-Voltage Positive Emitter-Coupled Logic (LVPECL) is another differential I/O standard. It requires
that one data bit is carried through two signal lines. Like LVDS, two pins are needed. It also requires
external resistor termination. The voltage swing between these two signal lines is approximately 850 mV.
The LVPECL circuit is similar to the LVDS scheme. It requires four external resistors, three for the driver
and one for the receiver. The values for the three driver resistors are different from that of LVDS since the
output voltage levels are different. Please note that the VOH levels are 200 mV below the standard
LVPECL levels.
Figure 2-26 LVPECL Board-Level Implementation
187
Ω
100
Ω
ZO = 50
Ω
ZO = 50
Ω
100
Ω
100
Ω
+
–
P
N
P
N
INBUF_LVPECL
OUTBUF_LVPECL
FPGA
Table 2-59 DC Input and Output Levels
DC Parameter
Min.
Typ.
Max.
Units
Min.
Max.
Min.
Max.
Min.
Max.
VCCI
3
3.3
3.6
V
VOH
1.8
2.11
1.92
2.28
2.13
2.41
V
VOL
0.96
1.27
1.06
1.43
1.3
1.57
V
VIH
1.49
2.72
1.49
2.72
1.49
2.72
V
VIL
0.86
2.125
0.86
2.125
0.86
2.125
V
Differential Input
Voltage
0.3
V
Table 2-60 AC Waveforms, Measuring Points, and Capacitive Loads
Input Low (V)
Input High (V)
Measuring Point* (V)
1.6 – 0.3
1.6 + 0.3
1.6
Note:
* Measuring Point = VTRIP