155Mbps to 622Mbps SFF/SFP
Laser Driver with Extinction Ratio Control
VCC
TX_DISABLE
POR AND COUNTER
60ms DELAY
PC_MON
RPC_MON
BC_MON
RBC_MON
COUNTER
60ms DELAY
VCC
IMD
1
VREF
VCC
COMP
IBIAS
82
VREF
EXCESSIVE
APC CURRENT
SETPOINT
COMP
EXCESSIVE
MOD CURRENT
SETPOINT
100ns DELAY
IMOD
ENABLE
IBIAS
ENABLE
R
Q
RS
LATCH
S
CMOS
SHUTDOWN
TX_FAULT
TTL
OPEN COLLECTOR
Figure 5. Simplified Safety Circuit
Table 1. Typical Fault Conditions
1
If any of the I/O pins are shorted to GND or VCC (single-point failure; see Table 2), and the bias current or the photocurrent
exceeds the programmed threshold.
2 End-of-life (EOL) condition of the laser diode. The bias current and/or the photocurrent exceed the programmed threshold.
3 Laser cathode is grounded and photocurrent exceeds the programming threshold.
4
No feedback for the APC loop (broken interconnection, defective monitor photodiode), and the bias current exceeds the
programmed threshold.
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