Datasheet

DS1878
SFP+ Controller with Digital LDD Interface
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LO, LOS LO, and MON1–MON4 LO alarms and warn-
ings. In addition, TXP LO is disabled from creating
FETG. See the Transmit Fault (TXFOUT) Output section
for a detailed explanation of TXFOUT. Figure 15 shows
that the same signals and faults can also be used to
generate the internal signal FETG (Table 01h/05h,
Registers FAh–FBh). FETG is used to send a fast “turn-
off” command to the laser driver. The status of FTEG
can be read (Lower Memory, Register 71h). The intend-
ed use is a direct connection to the Maxim laser driver’s
TXD input if this is desired. When V
CC
< POA, TXDOUT
is high impedance.
Transmit Fault (TXFOUT) Output
TXFOUT can be triggered by TXF input and all alarms,
warnings, and quick trips (Figure 16). The six ADC
alarms, warnings, and the LOS quick trips require
enabling (Table 01h/05h, Registers F8h, FCh–FDh). See
Figures 17a and 17b for nonlatched and latched opera-
tion. Latching of the alarms is controlled by the CNFGB
and CNFGC registers (Table 02h, Registers 8Ah–8Bh).
INVRSOUT
RSELC
RSEL
RSELS
IN1S
RSELOUT
LOSC
MUX
LOS LO
RXL
SETLOSCTL
LOS
INV LOS
IN1
LOSOUT
PINS
Figure 16. Logic Diagram 2
C
C
D
Q
Q
S
R
OUT IN
TXDS
R
PU
TXFS
TXFOUTS
SET BIAS REGISTER
AND MODULATION
REGISTER TO 0
TXD
TXFINT
TXP HI FLAG
TXP HI ENABLE
BIAS MAX
BIAS MAX ENABLE
HBAL FLAG
HBAL ENABLE
TXP LO FLAG
TXP LO ENABLE
t
INITR1
TXDC
V
CC
TXD
TXDOUT
TXDIO
TXDFG
FETG
TXDFLT
FAULT RESET TIMER
(130ms)
IN
OUT
POWER-ON
RESET
PINS
INVTXF
TXF
TXFOUT
Figure 15. Logic Diagram 1