82P33731_16 Datasheet, PDF (47/68 Pages) IDEA.lnc. – Synchronous Ethernet

82P33731 Datasheet
Table 25: LVPECL Input Port Electrical Characteristics
Parameter
Description
V_IL
Input Low Voltage, Differential Inputs
V_IH
Input High Voltage, Differential Inputs
V_ID
Input Differential Voltage
V_{IL_S}
Input Low Voltage, Single-ended Input
V_{IH_S}
Input High Voltage, Single-ended Input
I_IH
Input High Current, Input Differential Voltage V_ID = 1.4 V
I_IL
Input Low Current, Input Differential Voltage V_ID = 1.4 V
Note:
1. Assuming a differential input voltage of at least 100 mV.
2. Unused differential input terminated to VDD-1.4 V.
Min
VDD - 2.5
VDD - 2.4
0.1
VSS
VDD - 1.3
-10
Typ
VDD - 1.5
VDD - 1.4
0.7
VDD - 1.95
VDD - 0.9
Max
VDD - 0.5
VDD - 0.4
1.4
VDD - 1.5
VDD
10
Unit
Test Condition
V
V
V
V
V
A
A
8.3.3.2
LVPECL Output Port
8.3.3.2.1 LVPECL Termination for 3.3 V
The clock layout topology shown below is a typical termination for
LVPECL outputs. The two different layouts mentioned are recom-
mended only as guidelines.
The differential outputs are low impedance follower outputs that gen-
erate ECL/LVPECL compatible outputs. Therefore, terminating resistors
(DC current path to ground) or current sources must be used for func-
tionality. These outputs are designed to drive 50 transmission lines.
Matched impedance techniques should be used to maximize operating
frequency and minimize signal distortion. Figure 25 and Figure 26 show
two different layouts which are recommended only as guidelines. Other
suitable clock layouts may exist and it would be recommended that the
board designers simulate to guarantee compatibility across all printed
circuit and clock component process variations.
3.3V
LVPECL
3.3V
R3
R4
125Ω
125Ω
3.3V
Z_o = 50Ω
+
Z_o = 50Ω
R1
84Ω
_
R2
84Ω
Input
Figure 25. 3.3V LVPECL Output Termination
3.3V
Z_o = 50Ω
3.3V
+
LVPECL
Z_o = 50Ω
R1
50Ω
RTT =
1
((V_OH + V_OL) / (V_CC – 2)) – 2
* Z_o
_
Input
R2
50Ω
V_CC - 2V
RTT
Figure 26. 3.3V LVPECL Output Termination
©2016 Integrated Device Technology, Inc.
47
Revision 5, December 8, 2016