SY55857LKGTR MICREL [Micrel Semiconductor], SY55857LKGTR Datasheet - Page 7

• Manufacturer Part Number: SY55857LKGTR
• Description: 3.3V, 2.5Gbps ANY INPUT-to-LVPECL DUAL TRANSLATOR
• Manufacturer: MICREL [Micrel Semiconductor]

Micrel, Inc.
emitter), and small signal swing which results in low EMI.
LVPECL is ideal for driving 50
impedance transmission lines. There are several
techniques in terminating the LVPECL output, as shown
in Figures 13 through 15.
Notes:
1. For +2.5V systems: R1 = 250 , R2 = 62.5 .
2. For +3.3V systems: R1 = 130 , R2 = 82 .
Notes:
1. Power-saving alternatives to Thevenin termination.
2. Place termination resistors as close to destination inputs as possible.
3. Rb resistor sets the DC bias voltage, equal to V
4. C1 is an optional bypass capacitor intended to compensate for any t
M9999-082306
[e-mail] or [phone]
Figure 13. Parallel Termination-Thevenin Equivalent
“source”
LVPECL OUTPUT TERMINATION
Notes:
1. Power saving alternative to Thevenin termination.
2. Place termination resistors as close to destination inputs as possible.
3. Rb resistor sets the DC bias voltage, equal to VT.
LVPECL output have very low output impedance (open
For +2.5V systems: R
For +3.3V systems: R
mismatches.
+3.3V*
+3.3V
SY58021U
SY58021U
*Note. For +2.5V systems,
Figure 14. Three-Resistor “Y-Termination”
R1 = 250
Z
Z
Z = 50
Z = 50
O
O
R2 = 62.5
= 50
= 50
b
b
= 19 .
= 46 to 50 .
R1
130
50
R2
82
50
+3.3V*
* For +2.5V, R b = 19
* For +3.3V, R b = 46 to 50
R
50
b
*
and 100 -controlled
R1
130
R2
82
“destination”
+3.3V
T
.
V
DD
V
T
C1 (optional)
0.01 F
+3.3V*
= V
CC
–2V
r
/t
f
7
Notes:
1. Unused output (/Q) must be terminated to balance the output.
2. For +2.5V systems: R1 = 250 , R2 = 62.5 , R3 = 1.25k , R4 =
3. Unused output pairs (Q and /Q) may be left floating.
1.2k .
For +3.3V systems: R1 = 130 , R2 = 82 , R3 = 1k , R4 = 1.6k .
+3.3V*
*Note:
For +2.5V systems,
R1 = 250
SY58021U
Figure 15. Terminating Unused I/O
R2 = 62.5
Z
Z
O
O
= 50
= 50
R1
130
R2
82
+3.3V*
R1
130
R2
82
V
T
+3.3V*
= V
SuperLite™
SY55857L
CC
–2V