+3.3V, 622Mbps SDH/SONET

Laser Driver with Current Monitors and APC

6

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NAME

FUNCTION

1, 2, 6, 15,

17, 20, 24

Positive Supply Voltage

29

APCSET

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

100k

Ω resistor from this pad to ground if APC is not used.

PIN

3

DATA+

Positive PECL Data Input

4

DATA-

Negative PECL Data Input

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.

31

MODSET

Modulation Set Resistor. A resistor from this pad to ground sets the laser modulation current.

5, 10, 14, 21,

22, 30

GND

Ground

12, 13, 26,

27, 28

N.C.

No Connection. Leave unconnected.

11

FAIL

TTL Output. Indicates APC failure when low. Internally pulled high through a 6k

Ω resistor.

9

ENABLE

TTL/CMOS Enable Input. High for normal operation, low to disable laser bias and modulation

currents. Internally pulled high.

16

BIAS

Laser Bias Current Output. Isolate from laser with a ferrite bead.

19

OUT-

Ω resistor.

18

OUT+

Connect this pad to AC-coupling network.

23

MD

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.

25

CAPC

APC Compensation Capacitor. A 0.1µF capacitor connected from this pad to ground controls

the dominant pole of the APC feedback loop.

Pin Description

7

BIASMON

Sink Current Source—proportional to the laser bias current.

8

MODMON

Sink Current Source—proportional to the laser modulation current.