Rainbow Electronics MAX3738 User Manual

General Description

The MAX3738 is a +3.3V laser driver designed for mul­tirate transceiver modules with data rates from 1Gbps
to 2.7Gbps. Lasers can be DC-coupled to the
MAX3738 for reduced component count and ease of
multirate operation.

Laser extinction ratio control (ERC) combines the features
of automatic power control (APC), modulation compensa­tion, and built-in thermal compensation. The APC loop
maintains constant average optical power. Modulation
compensation increases the modulation current in pro­portion to the bias current. These control loops, com­bined with thermal compensation, maintain a constant
optical extinction ratio over temperature and lifetime.

The MAX3738 accepts differential data input signals.
The wide 5mA to 60mA (up to 85mA AC-coupled) mod­ulation current range and up to 100mA bias current
range, make the MAX3738 ideal for driving FP/DFB
lasers in fiber optic modules. External resistors set the
required laser current levels. The MAX3738 provides
transmit disable control (TX_DISABLE), single-point
fault tolerance, bias-current monitoring, and photocur­rent monitoring. The device also offers a latched failure
output (TX_FAULT) to indicate faults, such as when the
APC loop is no longer able to maintain the average
optical power at the required level. The MAX3738 is
compliant with the SFF-8472 transmitter diagnostic and
SFP MSA timing requirements.

The MAX3738 is offered in a 4mm x 4mm, 24-pin thin
QFN package and operates over the extended -40°C to
+85°C temperature range.

Applications

Multirate OC-24 to OC-48 FEC Transceivers
Gigabit Ethernet SFF/SFP and GBIC

Transceivers
1Gbps/2Gbps Fibre Channel SFF/SFP and GBIC

Transceivers

Features

♦ Single +3.3V Power Supply

♦ 47mA Power-Supply Current

♦ 85mA Modulation Current

♦ 100mA Bias Current

♦ Automatic Power Control (APC)

♦ Modulation Compensation

♦ On-Chip Temperature Compensation

♦ Self-Biased Inputs for AC-Coupling

♦ Ground-Referenced Current Monitors

♦ Laser Shutdown and Alarm Outputs

♦ Enable Control and Laser Safety Feature

MAX3738

1Gbps to 2.7Gbps SFF/SFP Laser Driver with

Extinction Ratio Control

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3162; Rev 0; 1/04

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART

TEMP

RANGE

PIN­PACKAGE

PKG
CODE

MAX3738ETG

T2444-1

BIAS

APCFILT2

V

CC

V

CC

TX_DISABLE

MODTCOMP

TH_TEMP

OUT+

APCFILT1

SHUTDOWN

GND

BC_MON

TX_FAULT

GND

V

CC

V

CC

MD

MODSET

APCSET

1

2

3

4

5

6

7891011 12

24 23 22 21 20 19

13

14

15

16

17

18

TOP VIEW

THE EXPOSED PADDLE MUST BE SOLDERED TO SUPPLY
GROUND ON THE CIRCUIT BOARD.

IN+

IN-

PC_MON

OUT-

MODBCOMP

MAX3738

Pin Configuration

Typical Application Circuit appears at end of data sheet.

-40°C to 85°C 24 Thin QFN

MAX3738

1Gbps to 2.7Gbps SFF/SFP Laser Driver with
Extinction Ratio Control

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +2.97V to +3.63V, TA= -40°C to +85°C. Typical values are at VCC= +3.3V, I

BIAS

= 60mA, I

MOD

= 60mA, TA= +25°C, unless

otherwise noted.) (Notes 1, 2)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

Supply Voltage VCC...............................................-0.5V to +6.0V

IN+, IN-, TX_DISABLE, TX_FAULT, SHUTDOWN,

BC_MON, PC_MON, APCFILT1, APCFILT2,
MD, TH_TEMP, MODTCOMP, MODBCOMP,

MODSET, and APCSET Voltage.............-0.5V to (V

CC

+ 0.5V)

OUT+, OUT-, BIAS Current.............................-20mA to +150mA

Continuous Power Dissipation (T

A

= +85°C)

24-Pin TQFN (derate 20.8mW/°C above +85°C) .......1805mW

Operating Junction Temperature Range...........-55°C to +150°C

Storage Temperature Range .............................-55°C to +150°C

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

POWER SUPPLY

Supply Current I

CC

(Note 3) 47 60 mA

Power-Supply Noise Rejection PSNR f ≤ 1MHz, 100mA

P-P

(Note 4) 33 dB

I/O SPECIFICATIONS

Differential Input Swing V

ID

DC-coupled, Figure 1 0.2 2.4

V

P-P

Common-Mode Input V

CM

1.7

V

CC

­V

LASER BIAS

Bias-Current-Setting Range 1

mA
Bias Off Current TX_DISABLE = high 0.1 mA
Bias-Current Monitor Ratio I

BIAS

/ I

BC_MON

68 79 95

mA/mA

LASER MODULATION

Modulation Current-Setting
Range

I

MOD

(Note 5) 5 85 mA

Output Edge Speed

20% to 80%
(Notes 6, 7)

5mA ≤ I

MOD

≤ 85mA 65 80 ps

Output Overshoot/Undershoot With 1pF between OUT+ and OUT- ±6%
Random Jitter (Notes 6, 7) 0.62 1.3

ps

RMS

2.7Gbps, 5mA ≤ I

MOD

≤ 85mA 18 40

Deterministic Jitter (Notes 6, 8)

1.25Gbps, 5mA ≤ I

MOD

≤ 85mA 20 41

ps

P-P

5mA ≤ I

MOD

≤ 10mA

Modulation-Current Temperature
Stability

(Note 6)

ppm/°C

5mA ≤ I

MOD

≤ 10mA

Modulation-Current-Setting Error

15Ω load,
T

A

= +25°C

%

Modulation Off Current TX_DISABLE = high 0.1 mA

AUTOMATIC POWER AND EXTINCTION RATIO CONTROLS

Monitor-Diode Input Current
Range

I

MD

Average current into the MD pin 18

µA

MD Pin Voltage 1.4 V
MD Current Monitor Ratio IMD / I

PC_MON

0.85 0.93

mA/mA

10mA ≤ I

10mA < I

≤ 85mA ±125 ±480

MOD

≤ 85mA ±15

MOD

±175 ±600

VID / 4

100

±20

1500

1.15

MAX3738

1Gbps to 2.7Gbps SFF/SFP Laser Driver with

Extinction Ratio Control

_______________________________________________________________________________________ 3

Note 1: AC characterization is performed using the circuit in Figure 2 using a PRBS 223- 1 or equivalent pattern.
Note 2: Specifications at -40°C are guaranteed by design and characterization.
Note 3: Excluding I

BIAS

and I

MOD

. Input data is AC-coupled. TX_FAULT open, SHUTDOWN open.

Note 4: Power-supply noise rejection (PSNR) = 20log

10(Vnoise (on VCC

) / ∆V

OUT

). V

OUT

is the voltage across the 15Ω load when IN+

is high.

Note 5: The minimum required voltage at the OUT+ and OUT- pins is +0.75V.
Note 6: Guaranteed by design and characterization.
Note 7: Tested with 00001111 pattern at 2.7Gbps.
Note 8: DJ includes pulse-width distortion (PWD).

PARAMETER

SYMBOL

CONDITIONS MIN TYP

MAX

UNITS

APC Loop Time Constant

3.3 µs

APC Setting Stability (Note 6)

ppm/°C

APC Setting Accuracy TA = +25°C

%

I

MOD

Compensation-Setting

Range by Bias

KK = ∆I

MOD

/ ∆I

BIAS

0 1.5

mA/mA

I

MOD

Compensation-Setting

Range by Temperature

TC TC = ∆I

MOD

/ ∆T (Note 6) 0 1.0

mA/°C

Threshold-Setting Range for
Temperature Compensation

T

TH

(Note 6) +10

°C

LASER SAFETY AND CONTROL

Bias and Modulation Turn-Off
Delay

C

APC_FILT

= 0.01µF, ∆IMD / ∆I

BIAS

= 1/80

(Note 6)

5µs

Bias and Modulation Turn-On
Delay

C

APC_FILT

= 0.01µF, ∆IMD / ∆I

BIAS

= 1/80

(Note 6)

µs

V

REF

Figure 5 1.14 1.3

V

INTERFACE SIGNALS

TX_DISABLE Input High V

HI

2.0 V

TX_DISABLE Input Low V

LO

R

PULL

= 45kΩ (typ) 0.8 V

VHI = V

CC

15

TX_DISABLE Input Current

V

LO

= GND -70

µA

TX_FAULT Output Low Sinking 1mA, open collector 0.4 V
Shutdown Output High Sourcing 100µA

V

Shutdown Output Low Sinking 100µA 0.4 V

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +2.97V to +3.63V, TA= -40°C to +85°C. Typical values are at VCC= +3.3V, I

BIAS

= 60mA, I

MOD

= 60mA, TA= +25°C, unless

otherwise noted.) (Notes 1, 2)

Threshold Voltage at Monitor Pins

C

APC_FILT

= 0.01µF, ∆IMD / ∆I

BIAS

= 1/70

±100 ±480

±15

+60

600

1.39

VCC - 0.4

-140

MAX3738

1Gbps to 2.7Gbps SFF/SFP Laser Driver with
Extinction Ratio Control

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VCC= +3.3V, C

APC

= 0.01µF, I

BIAS

= 20mA, I

MOD

= 30mA, TA= +25°C, unless otherwise noted.)

OPTICAL EYE DIAGRAM

(2.7Gbps, 2

7

- 1 PRBS, 2.3GHz FILTER)

MAX3738 toc01

54ps/div

1310nm FP LASER

r

e

= 8.2dB

OPTICAL EYE DIAGRAM

(1.25Gbps, 2

7

- 1 PRBS, 940MHz FILTER)

MAX3738 toc02

116ps/div

1310nm FP LASER

r

e

= 8.2dB

ELECTRICAL EYE DIAGRAM

(I

MOD

= 30mA, 2.7Gbps, 27 - 1 PRBS)

MAX3738 toc03

52ps/div

75mV/div

1pF BETWEEN OUT+

AND OUT-

SUPPLY CURRENT (ICC) vs. TEMPERATURE

(EXCLUDES BIAS AND MODULATION CURRENTS)

MAX3738 toc04

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

80706050403020100-10-20-30

35

40

45

50

55

60

30

-40 90

3.63V

2.97V

3.3V

BIAS-CURRENT MONITOR RATIO

vs. TEMPERATURE

MAX3738 toc05

TEMPERATURE (°C)

I

BIAS

/I

BC_MON

(mA/mA)

807050 60-10 0 10 20 30 40-30 -20

72

74

76

78

80

82

84

86

88

90

70

-40 90

PHOTOCURRENT MONITOR RATIO

vs. TEMPERATURE

MAX3738 toc06

TEMPERATURE (°C)

I

MD

/I

PC_MON

(mA/mA)

807050 60-10 0 10 20 30 40-30 -20

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

0.80

-40 90

MODULATION CURRENT vs. R

MODSET

MAX3738 toc07

R

MODSET

(kΩ)

I

MOD

(mA)

10

10

20

30

40

50

60

70

80

90

0

1100

PHOTODIODE CURRENT vs. R

APCSET

MAX3738 toc08

R

APCSET

(kΩ)

I

MD

(mA)

101

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0

0.1 100

DETERMINISTIC JITTER

vs. MODULATION CURRENT

MAX3738 toc09

I

MOD

(mA)

DJ (ps

P-P

)

807050 6020 30 4010

5

10

15

20

25

30

35

40

45

50

0

090

2.7Gbps

MAX3738

1Gbps to 2.7Gbps SFF/SFP Laser Driver with

Extinction Ratio Control

_______________________________________________________________________________________ 5

RANDOM JITTER

vs. MODULATION CURRENT

MAX3738 toc10

I

MOD

(mA)

RJ (ps

RMS

)

807050 6020 30 4010

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0

090

COMPENSATION (K) vs. R

MODBCOMP

MAX3738 toc11

R

MODBCOMP

(kΩ)

K (mA/mA)

1010.10.01

0.1

1

10

0.01

0.001 100

TEMPERATURE COMPENSATION vs.

R

TH_TEMP

(R

MODTCOMP

= 500Ω)

MAX3738 toc12

TEMPERATURE (°C)

I

MOD

(mA)

80706050403020100

40

50

60

70

80

90

100

30

-10 90

R

TH_TEMP

= 12k

Ω

R

TH_TEMP

= 7k

Ω

R

TH_TEMP

= 4k

Ω

R

TH_TEMP

= 2k

Ω

TEMPERATURE COMPENSATION vs.

R

TH_TEMP

(R

MODTCOMP

= 10kΩ)

MAX3738 toc13

TEMPERATURE (°C)

I

MOD

(mA)

80706050403020100

32

34

36

38

40

42

44

30

-10 10090

R

TH_TEMP

= 12k

Ω

R

TH_TEMP

= 7k

Ω

R

TH_TEMP

= 4k

Ω

R

TH_TEMP

= 2k

Ω

HOT PLUG WITH TX_DISABLE LOW

MAX3738 toc14

20ms/div

V

CC

FAULT

TX_DISABLE

LASER

OUTPUT

0V

3.3V

t_init = 59.6ms

LOW

LOW

TRANSMITTER ENABLE

MAX3738 toc15

10µs/div

V

CC

FAULT

TX_DISABLE

LASER

OUTPUT

3.3V

t_on = 23.8µs

LOW

HIGH

LOW

TRANSMITTER DISABLE

MAX3738 toc16

20ns/div

V

CC

FAULT

TX_DISABLE

LASER

OUTPUT

3.3V

91.2ns

LOW

HIGH

LOW

RESPONSE TO FAULT

MAX3738 toc17

400ns/div

V

PC_MON

FAULT

TX_DISABLE

LASER

OUTPUT

t_fault = 160ns

EXTERNALLY

FORCED FAULT

FAULT RECOVERY TIME

MAX3738 toc18

40ms/div

V

PC_MON

FAULT

TX_DISABLE

LASER

OUTPUT

t_init = 58ms

EXTERNALLY
FORCED FAULT

LOW

LOWLOW

HIGH

HIGH

Typical Operating Characteristics (continued)

(VCC= +3.3V, C

APC

= 0.01µF, I

BIAS

= 20mA, I

MOD

= 30mA, TA= +25°C, unless otherwise noted.)