Rainbow Electronics MAX3738 - Manual (Page 6)

MAX3738
1Gbps to 2.7Gbps SFF/SFP Laser Driver with
Extinction Ratio Control
6 _______________________________________________________________________________________
PIN NAME FUNCTION
1 MODTCOMP
Modulation-Current Compensation from Temperature. A resistor at this pin sets the temperature
coefficient of the modulation current when above the threshold temperature. Leave open for zero
temperature compensation.
2, 5, 14,
17
V CC +3.3V Supply Voltage
3 IN+ Noninverted Data Input
4 IN- Inverted Data Input
6 TX_DISABLE
Transmitter Disable, TTL. Laser output is disabled when TX_DISABLE is asserted high or left
unconnected. The laser output is enabled when this pin is asserted low.
7 PC_MON
Photodiode-Current Monitor Output. Current out of this pin develops a ground-referenced voltage
across an external resistor that is proportional to the monitor diode current.
8 BC_MON
Bias-Current Monitor Output. Current out of this pin develops a ground-referenced voltage across an
external resistor that is proportional to the bias current.
9 SHUTDOWN
Shutdown Driver Output. Voltage output to control an external transistor for optional shutdown
circuitry.
10, 12 GND Ground
11 TX_FAULT Open-Collector Transmit Fault Indicator (Table 1)
13 BIAS Laser Bias-Current Output
15 OUT- Inverted Modulation-Current Output. IMOD flows into this pin when input data is low.
16 OUT+ Noninverted Modulation-Current Output. IMOD flows into this pin when input data is high.
18 MD
Monitor Photodiode Input. Connect this pin to the anode of a monitor photodiode. A capacitor to
ground is required to filter the high-speed AC monitor photocurrent.
19 APCFILT1
Connect a capacitor (CAPC) between pin 19 (APCFILT1) and pin 20 (APCFILT2) to set the dominant
pole of the APC feedback loop.
20 APCFILT2 (See pin 19)
21 APCSET A resistor connected from this pin to ground sets the desired average optical power.
22 MODSET
A resistor connected from this pin to ground sets the desired constant portion of the
modulation current.
23 MODBCOMP
Modulation-Current Compensation from Bias. Couples the bias current to the modulation current.
Mirrors IBIAS through an external resistor. Leave open for zero-coupling.
24 TH_TEMP
Threshold for Temperature Compensation. A resistor at this pin programs the temperature above
which compensation is added to the modulation current.
EP Exposed Pad
Ground. Solder the exposed pad to the circuit board ground for specified thermal and electrical
performance.
Pin Description