Datasheet

LOS
TXF
TXDOUT
TXD
FAULT
DISABLE
RSEL
RSELOUT
LOS
LOSOUT
TXFOUT TX_FAULT
SDA
SCL
MODE_DEF2 (SDA)
RATE SELECT
LOS
MODE_DEF1 (SCL)
TX_DISABLE
MODE
DAC
BIAS
DAC
LDD
EEPROM
QUICK
TRIP
LOS
ADC
I
2
C
3W
3W
CS1
DS1878
MAX3946
3W
CS2
MAX3945
MON1
MON2
MON3
BMON
R
MON
680Ω
+3.3V
R
BD
LA
PIN-ROSA
DFB TOSA
DS1878
SFP+ Controller with Digital LDD Interface
12 ______________________________________________________________________________________
Detailed Description
The DS1878 integrates the control and monitoring func-
tionality required to implement a VCSEL-based or DFB-
based SFP or SFP+ system using Maxim’s limiting
amplifiers and laser drivers. Key components of the
device are shown in the Block Diagram and described
in subsequent sections.
3-Wire DAC Control
The device controls two 9-bit DACs inside the Maxim
laser drivers. One DAC is used for laser bias control,
while the other is used for modulation amplitude control.
The device communicates with the laser driver over a 3-
wire digital interface (see the 3-Wire Master for
Controlling the Maxim Laser Driver section). The com-
munication between the device and Maxim laser driver
and/or limiting amplifier is transparent to the end user.
Typical Operating Circuit