Table 1. typical fault conditions – Rainbow Electronics MAX3738 User Manual
Page 9
MAX3738
1Gbps to 2.7Gbps SFF/SFP Laser Driver with
Extinction Ratio Control
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9
1
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.
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.
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