+3.3V, 2.5Gbps Low-Power Laser Driver

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7

Pin Description

PIN

NAME

FUNCTION

1, 4, 13, 15, 18

Power-Supply Voltage

2

DATA+

Noninverting Data Input, with On-Chip Biasing

3

DATA-

Inverting Data Input, with On-Chip Biasing

5

CLK+

Noninverting Clock Input for Data Retiming, with On-Chip Biasing

6

CLK-

Inverting Clock Input for Data Retiming, with On-Chip Biasing

7, 9, 12

GND

Ground

8

LATCH

Data Retiming Enable Input, Active-High. Retiming disabled when floating or pulled low.

10

EN

TTL/CMOS Enable Input. Low for normal operation. Float or pull high to disable laser bias and

modulation currents. Internal 100k

11

MODSET

A resistor connected from this pin to ground sets the desired modulation current.

14

BIAS

Laser Bias Current Output. Connect to the laser through an inductor.

16

OUT+

17

OUT-

Negative Modulation-Current Output. Current flows into this pin when input data is low. Connect

to load equivalent to that on OUT+ to maintain differential output balance.

19

MD

Monitor Diode Input. Connect this pin to the anode of the monitor diode. Leave floating for

open-loop operation.

20

APCFILT1

A capacitor between APCFILT1 and APCFILT2 sets the dominant pole of the APC feedback

21

APCFILT2

See above.

22

FAIL

TTL/CMOS Failure Output, Active-Low. Indicates APC failure when low.

23

APCSET

A resistor connected from this pin to ground sets the desired average optical power. Connect a

100k

Ω resistor to GND for open-loop operation.

24

BIASMAX

A resistor connected from this pin to ground sets the maximum bias current. The APC function

can subtract current from this maximum value, but cannot add to it. For open-loop operation,

this pin sets the laser bias current.

EP

EXPOSED

PAD

Ground. Solder this pad to ground.