
MAX3646
155Mbps to 622Mbps SFF/SFP
Laser Driver with Extinction Ratio Control
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If any of the I/O pins are shorted to GND or V
CC
(single-point failure; see Table 2), and the bias current or the photocurrent
exceeds the programmed threshold.
End-of-life (EOL) condition of the laser diode. The bias current and/or the photocurrent exceed the programmed threshold.
Laser cathode is grounded and photocurrent exceeds the programming threshold.
No feedback for the APC loop (broken interconnection, defective monitor photodiode), and the bias current exceeds the
programmed threshold.
Table 1. Typical Fault Conditions
R
BC_MON
BC_MON
V
CC
V
CC
R
PC_MON
PC_MON
COMP
V
REF
V
REF
TTL
OPEN COLLECTOR
CMOS
SHUTDOWN
TX_FAULT
R
S
Q
RS
LATCH
COUNTER
60ms DELAY
POR AND COUNTER
60ms DELAY
100ns DELAY
I
BIAS
ENABLE
I
MOD
ENABLE
V
CC
TX_DISABLE
COMP
EXCESSIVE
APC CURRENT
SETPOINT
EXCESSIVE
MOD CURRENT
SETPOINT
I
MD
1
I
BIAS
82
Figure 5. Simplified Safety Circuit
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