MAX3766EEP+ Maxim Integrated Products, MAX3766EEP+ Datasheet - Page 10

• Manufacturer Part Number: MAX3766EEP+
• Description: IC LASR DRVR 622MBPS 5.5V 20QSOP
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3766EEP+

• Data Rate: 622Mbps
• Number Of Channels: 1
• Voltage - Supply: 4.5 V ~ 5.5 V
• Current - Supply: 25mA
• Current - Modulation: 60mA
• Current - Bias: 80mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-QSOP
• Mounting Type: Surface Mount
• Operating Supply Voltage: 5 V
• Supply Current: 25 mA
• Maximum Operating Temperature: + 85 C
• Maximum Power Dissipation: 590 mW
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

This configuration is shown in the Typical Application
Circuits (configured for best performance), and can
be selected by connecting a capacitor (C
ground at SAFETY. In this configuration, the transmitter
is shut down when a failure is detected. It can be
restarted only by a power-on cycle or a toggle of the
ENABLE input.
During start-up, FAIL is asserted until laser power reach-
es the programmed level. The safety circuit must be dis-
abled at power-on or at transmitter enable, providing
enough time for the APC circuit to reach the programmed
laser power level.
In space-constrained designs, C
ed to provide a shutdown delay. When power is initially
applied, or when the ENABLE signal is toggled from a
logic 0 to a logic 1, the voltage at SAFETY is low, and
rises with a time constant set by C
nal 200kΩ pull-up resistor. The SAFETY signal is invert-
ed and resets the input of a reset-dominant RS flip-flop.
The internal signal FAILURE from the failure-detection
circuit is connected to the set input of the flip-flop. After
SAFETY has gone high (allowing time for the APC feed-
back loop to settle) and if internal signal FAILURE is low,
the flip-flop output is low, and the bias and modulation
outputs are allowed to remain on. Refer to Figure 5 for
a timing diagram of start-up in the latched shutdown
configuration.
622Mbps LAN/WAN Laser Driver with
Automatic Power Control and Safety Shutdown
Figure 4. Simplified Safety Circuit Schematic
10
C
SAFETY
______________________________________________________________________________________
SAFETY
ENABLE
Latched Shutdown Configuration
200k
100k
(INTERNAL)
FAILURE
V
CC
OPEN
COLLECTOR
SAFETY
SAFETY
can be select-
and an inter-
SAFETY
) to
OPEN
COLLECTOR
S
R
The duration of t
a successful start-up. After start-up, the transmitter
operates normally until a failure is detected, causing
the output currents to be shut down. The laser-current
outputs remain off until the failure condition is eliminat-
ed and the ENABLE input is toggled, or until the power
is cycled. A potential problem with this transmitter-
enable method is that a slow-rising power supply may
not enable the transmitter.
Figure 5. Start-Up Sequence Timing
V
LASER BIAS AND
MODULATION CURRENT
FAIL
OUTPUT
SAFETY
Q
CC
RESET DOMINATE
RS FLIP-FLOP
t
ON
V
SAFETY
CC
t
APC
t
SAFETY
ON (OR ENABLE SWITCHED TO ON STATE)
OUTPUT CURRENTS ENABLED AFTER A FIXED DELAY
FAIL
FAIL DEASSERTS WHEN THE APC LOOP SETTLES
must be about 10 times t
(INTERNAL)
SHDN
SAFETY FEATURES START CHECKING
THE FAILURE SIGNAL AFTER A TIME SET
BY A CAPACITOR ON THE SAFETY INPUT.
AFTER THIS TIME, THE LASER DRIVER IS
DISABLED IF A FAILURE OCCURS.
IN
SIMPLIFIED
OPEN-COLLECTOR
OUTPUT CIRCUIT
OUT
APC
for