afbr-820bz Avago Technologies, afbr-820bz Datasheet - Page 4

• Manufacturer Part Number: afbr-820bz
• Description: Twelve-channel Transmitter And Receiver Pluggable, Parallel-fiber-optic Modules
• Manufacturer: Avago Technologies

High Speed Signal Interface
Figure 3 shows the interface between an ASIC/SerDes and
the fiber Optic modules. For simplicity, only one channel is
shown. As shown in the Figure 3, the compliance points are
on the host board side of the electrical connectors.Sets of
s-parameters are defined for the transmitter and receiver
interfaces. The transmitter and receiver are designed,
when operating within Recommended Operating Con-
ditions, to provide a robust eye-opening at the receiver
outputs. See the Recommended Operating Conditions
and the Receiver Electrical Characteristics for details.
Unused inputs and outputs should be terminated with
100 : differential loads.
The transmitter inputs support a wide common mode
range and DC blocking capacitors may not be needed –
none are shown in Figure 3. Depending on the common
mode range tolerance of the ASIC/SerDes inputs, DC
blocking capacitors may be required in series with the
receiver. Differential impedances are nominally 100 :.
The common mode output impedance for the receiver is
nominally 25 : while the nominal common mode input
impedance of the transmitter is 25 :.
Figure 3. Application Reference Diagram
4
ASIC/SerDes
50 :
50 :
Host Board Electrical Interface
- Compliance Points -
CAC
CAC
SDD22
SCC22
SDC22
SDD11
SCC11
SCD11
Transmitter Input Equalization
Transmitter inputs can be programmed for one of several
levels of equalization. See Figure 4. The default case
provides a flat gain-frequency response in the inputs.
Different levels of compensation can be selected to
equalize skin-effect losses across the host circuit board.
See Tx Memory Map 01h Upper Page section addresses
228 - 233 for programming details.
Figure 4. Input Equalization
FO Tx (1 of 12 Lanes)
FO Rx (1 of 12 Lanes)
FO Rx Electrical Interface
FO Tx Electrical Interface
50 :
50 :
Frequency
No Equalization
Maximum Equalization