MAX3646 Maxim Integrated Products, MAX3646 Datasheet - Page 10

• Manufacturer Part Number: MAX3646
• Description: 155Mbps to 622Mbps Sff/sfp Laser Driver
• Manufacturer: Maxim Integrated Products

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155Mbps to 622Mbps SFF/SFP
Laser Driver with Extinction Ratio Control
Table 2. Circuit Responses to Various Single-Point Faults
*A fault state asserts the TX_FAULT pin, disables the modulation and bias currents, and asserts the SHUTDOWN pin.
10
TX_DISABLE Modulation and bias currents are disabled.
SHUTDOWN
TX_FAULT
APCFILT1
APCFILT2
BC_MON
PC_MON
MODSET
APCSET
OUT+
OUT-
BIAS
______________________________________________________________________________________
PIN
IN+
MD
IN-
Does not affect laser power.
The optical average power increases and a fault occurs
if V
responds by decreasing the bias current.
The optical average power decreases and the APC loop
responds by increasing the bias current. A fault state
occurs if V
This disables bias current. A fault state occurs.
Does not affect laser power. If the shutdown circuitry is
used, the laser current is disabled.
In this condition, the laser forward voltage is 0V and no
light is emitted.
The APC circuit responds by increasing the bias current
until a fault is detected, then a fault state* occurs.
Does not affect laser power.
Fault state* occurs.
Fault state* occurs.
I
voltage.
I
voltage.
Does not affect laser power.
Does not affect laser power.
BIAS
BIAS
PC_MON
CIRCUIT RESPONSE TO OVERVOLTATGE OR
increases until V
increases until V
BC_MON
exceeds the threshold. The APC loop
exceeds the threshold voltage.
SHORT TO V
BC_MON
BC_MON
exceeds the threshold
exceeds the threshold
CC
Does not affect laser power.
Normal condition for circuit operation.
The optical average power decreases and the APC loop
responds by increasing the bias current. A fault state
occurs if V
The optical average power increases and a fault occurs
if V
responds by decreasing the bias current.
The APC circuit responds by increasing the bias current
until a fault is detected, then a fault* state occurs.
Does not affect laser power.
Fault state* occurs. If the shutdown circuitry is used, the
laser current is disabled.
Fault state* occurs. If the shutdown circuitry is used, the
laser current is disabled.
Does not affect laser power.
Does not affect laser power.
Does not affect laser power.
I
voltage.
I
voltage.
Fault state* occurs.
Fault state* occurs.
BIAS
BIAS
PC_MON
CIRCUIT RESPONSE TO UNDERVOLTAGE OR
increases until V
increases until V
BC_MON
exceeds the threshold. The APC loop
SHORT TO GROUND
exceeds the threshold voltage.
BC_MON
BC_MON
exceeds the threshold
exceeds the threshold