+3.3V, 622Mbps SDH/SONET
Laser Driver with Current Monitors and APC
6 Maxim Integrated
MAX3669
PIN
TQFN-E P TQFP
NAME FUNCTION
1, 13, 16,
19
1, 2, 6, 15,
17, 20, 24
V
CC
Positive Supply Voltage
2 3 DATA+ Positive PECL Data Input
3 4 DATA- Negative PECL Data Input
4, 8, 11,
17, 22
5, 10, 14,
21, 22, 30
GND Ground
5 7 BIASMON Sink Current Source. Proportional to the laser bias current.
6 8 MODMON Sink Current Source. Proportional to the laser modulation current.
7 9 ENABLE
TTL/CMOS Enable Input. High for normal operation, low to disable laser bias and
modulation currents. Internally pulled high.
9 11 FAIL
TTL Output. Indicates APC failure when low. Internally pulled high through a 6k
10
12, 13, 26,
27, 28
N.C. No Connection. Leave unconnected.
12 16 BIAS Laser Bias Current Output. Isolate from laser with a ferrite bead.
14 18 OUT+
Positive Modulation Current Output. I
MOD
flows into this pad when the input signal is
high. Connect this pad to AC-coupling network.
15 19 OUT-
Negative Modulation Current Output. I
MOD
flows into this pad when the input signal is
low. Connect this pad to V
CC
through a 6.3 resistor.
18 23 MD
Monitor Photodiode Connection. Connect this pad to the monitor photodiode anode.
A capacitor to ground is required to filter high-speed AC monitor photocurrent.
20 25 CAPC
APC Compensation Capacitor. A 0.1μF capacitor connected from this pad to ground
controls the dominant pole of the APC feedback loop.
21 29 APCSET
APC Set Resistor. A resistor connected from this pad to ground sets the desired average
optical power. The resulting current is equal to the desired DC monitor diode current.
Connect a 100k resistor from this pad to ground if APC is not used.
23 31 MODSET
Modulation Set Resistor. A resistor from this pad to ground sets the laser modulation
current.
24 32 BIASMAX
Maximum Bias Set Resistor. A resistor from this pad to ground sets the maximum laser
bias current. The APC function can subtract from this maximum value but cannot add to
it. This resistor controls the bias-current level when the APC loop is not used.
— — EP Exposed Pad (TQFN only). The exposed paddle must be soldered to ground.
