SY89874U_08 Datasheet, PDF (9/10 Pages) Micrel Semiconductor – 2.5GHz ANY DIFF. IN-TO-LVPECL PROGRAMMABLE CLOCK DIVIDER

Micrel, Inc.
LVPECL OUTPUT TERMINATION RECOMMENDATIONS
+3.3V
+3.3V
R1
Z_O = 50Ω ^130Ω
Z_O = 50Ω
R2
82Ω
R1
130Ω +3.3V
R2
82Ω ^Vt ^{= V}CC ^—2V
Precision Edge^®
SY89874U
Figure 4a. Parallel Termination–Thevenin Equivalent
Note 1. For +2.5V systems: R1 = 250Ω, R2 = 62.5Ω
+3.3V
Z = 50Ω
Z = 50Ω
+3.3V
“source”
50Ω
50Ω
50Ω
“destination”
Rb
(Optional)
C1
0.01µF
Figure 4b. Three-Resistor “Y–Termination”
Note 1.
Note 2.
Note 3.
Note 4.
Power-saving alternative to Thevenin termination.
Place termination resistors as close to destination inputs as possible.
R_b resistor sets the DC bias voltage, equal to V_t. For +3.3V systems R_b = 46Ω to 50Ω. For +2.5V systems R_b = 39Ω
C1 is an optional bypass capacitor intended to compensate for any t_r/t_f mismatches.
+3.3V
+3.3V
+3.3V
Q
/Q
R1
130Ω
Z_O = 50Ω
V_t = V_CC —2V
R2
82Ω
R1
130Ω
R2
82Ω
R3 ^{Vt = VCC —1.3V}
1kΩ
+3.3V
R4
1.6kΩ
Figure 4d. Terminating Unused I/O
Note 1. Unused output (/Q) must be terminated to balance the output.
Note 2. For +2.5V systems: R1 = 250Ω, R2 = 62.5Ω, R3 = 1.25kΩ, R4 = 1.2kΩ.
M9999-031208
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