Datasheet

MAX3740A
3.2Gbps SFP VCSEL Driver with Diagnostic
Monitors
8 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1, 10, 13 GND Ground
2 TX_DISABLE
Transmit Disable. Driver output is disabled when TX_DISABLE is high or left unconnected. The
driver output is enabled when the pin is asserted low.
3 IN+ Noninverted Data Input
4 IN- Inverted Data Input
5 FAULT
Fault Indicator. Open-drain output with ESD protection. FAULT is asserted high during a
fault condition.
6 SQUELCH
Squelch Enable. Squelch is enabled when the pin is set high. Squelch is disabled when the pin is
set low or left open.
7, 16, 20 V
CC
+3.3V Supply Voltage
8 TC1
Temperature Compensation Set Pin 1. A resistor placed between TC1 and TC2 (R
TC
) programs the
temperature coefficient of the modulation current.
9 TC2
Temperature Compensation Set Pin 2. A resistor placed between TC1 and TC2 (R
TC
) programs the
temperature coefficient of the modulation current.
11 MODSET
Modulation Set. A resistor connected from MODSET to ground (R
MODSET
) sets the desired
modulation current amplitude.
12 PEAKSET
Peaking Current Set. A resistor connected between PEAKSET and ground (R
PEAKSET
) programs
the peaking current amplitude. To disable peaking, leave PEAKSET open.
14 OUT- Inverted Modulation-Current Output
15 OUT+ Noninverted Modulation-Current Output
17 BIASSET
Bias Current Set. When a closed-loop configuration is used, connect a 1.7k resistor between
ground and BIASSET to set the maximum bias current. When an open configuration is used,
connect a resistor between BIASSET and ground (R
BIASSET
) to program the VCSEL bias current.
18 BIAS Bias Current Output
19 BIASMON
Bias Current Monitor. The output of BIASMON is a sourced current proportional to the bias current.
A resistor connected between BIASMON and ground (R
BIASMON
) can be used to form a ground-
referenced bias monitor.
21 COMP
Compensation Pin. A capacitor between COMP and MD compensates the APC. A typical value of
0.047μF is recommended. For open-loop configuration, short the COMP pin to GND to deactivate
the APC.
22 MD Monitor Diode Connection
23 REF
Reference Pin. Reference monitor used for APC. A resistor between REF and MD (R
PWRSET
) sets the
photo monitor current when the APC loop is closed.
24 PWRMON
Average Power Monitor. The pin is used to monitor the transmit optical power. For open-loop
configuration, connect PWRMON to GND.
— EP
Exposed Pad. Ground. Must be soldered to the circuit board ground for proper thermal and
electrical performance. See the Layout Considerations section.