cx28250 Mindspeed Technologies, cx28250 Datasheet - Page 198

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

Appendix A PECL Applications
A.3 CX28250 to 5 V PMD Outputs
A-6
A.3 CX28250 to 5 V PMD Outputs
The recommended termination and level shifting circuit for connecting 5.0 V
PECL outputs to the CX28250 3.3 V PECL inputs is illustrated in
The line termination impedance is demonstrated in the following equation:
generally V
CX28250 is:
of 340 mV .
The outputs of the 5 V PECL should be biased at around V
If you select:
R
R
R
Z
Then the low level input voltage, V
This is well below the maximum of V
Given that the V
Not only is this above the minimum (V
0
6
7
8
= 50 Ω
= 82.5 Ω
= 56 Ω
= 75 Ω
Mindspeed Technologies
cc
-2.0. Therefore:
oh
for 5 V PECL is around V
V il
V
3.0V
=
ih
Z 0
----------------------------------- -
(
=
R
=
=
6
5.0
-----------------------
(
3.7
+
R
(
----------------------------------- -
(
(
------------------------------------- -
R
(
R
7
R
R
R
il
×
7
6
+
×
7
7
, going to the CX28250 is:
6
+
+
™
R
+
+
R
ref
R
+
8
ref
R
R
8
8
R
R
-0.06 V .
R
)
ATM Physical Interface (PHY) Devices
8
7
8
8
+0.06), but it provides a differential
7
)
+
)
)
=
×
+
×
R
=
R
R
cc
2.1V
V
8
6
8
)
1.76V
-1.3 V , then V
cc
)
ref
28250-DSH-002-C
ih
, which is
for the
Figure
CX28250
A-4.