V23818-K305-L56 Datasheet, PDF (5/6 Pages) Infineon Technologies AG – Small Form Factor Multimode 850 nm 1.0625 GBd Fibre Channel 1.3 Gigabit Ethernet 2x5 Transceiver with LC™ Connector

APPLICATION NOTES
EMI-Recommendation
To avoid electromagnetic radiation exceeding the required limits
please read the following recommendations:
Whenever high speed Gigabit switching components are
located on the PCB (also multiplexers, clock recoveries ...) any
opening of the machine may generate radiation even at differ-
ent locations. Thus every mechanical opening or aperture
should be as small as possible.
On the board itself every data connection should be an imped-
ance matched line (e.g. strip line, coplanar strip line). Data,
Datanot should be routed symmetrically, via's should be
avoided. A symmetrically matching resistor of 100 Ω should be
placed at the end of each matched line. An alternative termina-
tion can be provided with a 50 Ω resistor at each (D, Dn). In DC
coupled systems an artificial 50 Ω resistance can be achieved
as follows: For 3.3 V: 125 Ω to V_CC and 82 Ω to V_EE, for 5 V:
82 Ω to V_CC and 125 Ω to V_EE at Data and Datanot. Please con-
sider whether there is an internal termination inside an IC or a
transceiver.
It is recommended that chassis GND and signal GND should
remain separate if there are openings or apertures of the hous-
ing nearby. Sometimes signal GND is the most harmful source
of radiation. Connecting chassis GND and signal GND at the
plate/ bezel/ backside wall e.g. by means of a fiber optic trans-
ceiver may result in a huge amount of radiation. Even a capaci-
tive coupling between signal GND and chassis may be harmful
if it is to close to an opening or an aperture.
If a separation of signal GND and chassis GND is not possible,
it is strongly recommended to provide a proper contact
between signal GND and chassis GND at almost every location.
This concept is suitable to avoid hotspots. Hotspots are places
of highest radiation which could be generated if only a few con-
nections between signal and chassis GND are available. Com-
pensation currents would concentrate at these connections,
causing radiation.
For the SFF transceiver a connection of the 4 housing pins to
chassis GND is recommended. If no separate chassis GND is
available on the users PCB the pins should be connected to sig-
nal GND. In this case take care of the notes above.
Please consider that the PCB may behave like a waveguide.
With an ε_r of 4, the wavelength of the harmonics inside the
PCB will be half of that in free space. In this case even small
PCBs may have unexpected resonances.
Multimode 850 nm Gigabit Ethernet/Fibre Channel 2x5 Transceiver, AC/AC
VCSEL
Driver
100 Ω
Infineon Transceiver
V23818-K305-L56
Signal
Detect
VEEt 7
TD+ 9
TD- 10
TxDis 8
VCCt 6
C1
VCCr 2
C2
SD 3 TTL level
VCC SerDes
3.3 V
L1
VCC
3.3 V
L2
C3
SD to upper level
VCC
Tx+
ECL/PECL
Driver
Tx-
Serializer/
Deserializer
Gigabit
Transceiver
Chip
Pre-
Amp
Limiting
Amplifier
RD- 4
RD+ 5
VEEr 1
RD-
RD+
Receiver
PLL etc.
C1/2/3 = 4.7 µF
L1/2 = 1 µH
R1/2 = Depends on SerDes chip used
R3/4 = Depends on SerDes chip used
R7/8 = Biasing (depends on SerDes chip)
Place R1/2/3/4/7/8 close to SerDes chip
Place R5/6 close to Infineon transceiver
Values of R1/2/3/4 may vary as long as proper 50 Ω termination
to V_EE or 100 Ω differential is provided. The power supply filter-
ing is required for good EMI performance. Use short tracks
from the inductor L1/L2 to the module V_CCRx/V_CCTx.
The transceiver contains an automatic shutdown circuit. Reset
is only possible if the power is turned off, and then on again.
(V_CCTx switched below V_TH).
Application Board available on request.
Fiber Optics
V23818-K305-L56, SFF, MM 850nm 1.0625 GBd Fibre Channel, 1.3 GBE 2x5 Trx (LC™), ext.temp.
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