MAX3668_05 Datasheet, PDF (5/12 Pages) Maxim Integrated Products – +3.3V, 622Mbps SDH/SONET Laser Driver with Automatic Power Control

+3.3V, 622Mbps SDH/SONET
Laser Driver with Automatic Power Control
Typical Operating Characteristics (continued)
(V_CC = +3.3V, T_A = +25°C, unless otherwise noted.)
AVAILABLE BIAS CURRENT
vs. MAXIMUM BIAS SET RESISTOR
1000
V_CC = +3.3V, + 5V
100
DISTRIBUTION OF MODULATION CURRENT
STABILITY (WORST CASE)
25
T_A = -40°C TO +85°C
I_MOD = 5mA
20
DISTRIBUTION OF MONITOR DIODE CURRENT
STABILITY (WORST CASE)
25
T_A = -40°C TO +85°C
I_MD = 18µA
20
15
15
10
CLOSED-LOOP OPERATION
10
10
1
V_CC = +5V
V_CC = +3.3V
0.1
1.4 1.6 1.8 2.0 2.2 2.4 2.6
R_BIAS (kΩ)
5
0
-25 65 155 245 335 425 515
MODULATION DIODE CURRENT STABILITY (ppm/°C)
5
0
-88 -52 20 92 160
MONITOR DIODE CURRENT STABILITY (ppm/°C)
Pin Description
PIN
1, 2, 6, 15,
17, 20, 24
3
4
5, 7, 8, 10,
14, 21, 22, 30
9
11
12, 13, 26,
27, 28
16
18
19
23
25
NAME
V_CC
DATA+
DATA-
GND
ENABLE
FAIL
N.C.
BIAS
OUT+
OUT-
MD
CAPC
29
APCSET
31
MODSET
32
BIASMAX
FUNCTION
Positive Supply Voltage
Positive PECL Data Input
Negative PECL Data Input
Ground
TTL/CMOS Enable Input. High for normal operation, low to disable laser bias and modulation
currents. Internally pulled high.
TTL Output. Indicates APC failure when low. Internally pulled high through a 6kΩ resistor.
No Connection. Leave unconnected.
Laser Bias Current Output. Isolate from laser with a ferrite bead.
Positive Modulation Current Output. I_MOD flows into this pad when the input signal is high.
Connect this pad to AC coupling network.
Negative Modulation Current Output. I_MOD flows into this pad when the input signal is low.
Connect this pad to V_CC through a 6.3Ω resistor.
Monitor Photodiode Connection. Connect this pad to the monitor photodiode anode. A capaci-
tor to ground is required to filter high-speed AC monitor photocurrent.
APC Compensation Capacitor. A 0.1µF capacitor connected from this pad to ground controls
the dominant pole of the automatic power control (APC) feedback loop.
APC Set Resistor. A resistor connected from this pad to ground sets the desired average opti-
cal power. The resulting current is equal to the desired DC monitor diode current. Connect a
100kΩ resistor from this pad to ground if APC is not used.
Modulation Set Resistor. A resistor from this pad to ground sets the laser modulation current.
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.
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