cx28250 Mindspeed Technologies, cx28250 Datasheet - Page 193

• Manufacturer Part Number: cx28250
• Description: Cx28250 Atm Physical Interface Phy Devices
• Manufacturer: Mindspeed Technologies

28250-DSH-002-C
Appendix A PECL Applications
This section provides application examples for the PECL interface.
A.1 CX28250 to 3.3 V PMD
If using a PMD that does not output a low level voltage (sink current during a
logic 0) the network shown in
must satisfy two equations.
frequency current, resistors R
ignoring the extremely high impedance of the PECL input.
where: Z
network should be as close to the destination as possible. An overview of circuit
board trace impedance is given in
low-level voltage.
First, since the Vcc supply and ground both provide a path for the high
Second, R
For example: if Z
then R
0
Mindspeed Technologies
1
is the characteristic impedance of the circuit board trace. This matching
= 100 Ω and R
1
and R
0
2
= 50 Ω, V
form a voltage divider network that establishes the
2
= 100 Ω.
1
A
Figure A-1
and R
il
V
Z
il
0
Section
= 1.65 V, and V
=
=
2
are treated as if they were in parallel,
-----------------------
(
-----------------------
(
V
R
R
R
™
cc
1
1
1
should be used. Resistors R
3.2.2.
×
+
+
×
R
R
R
R
2
2
2
2
)
)
cc
= 3.3 V
1
and R
2
A-1