Analog Devices ADN2870 Datasheet

3.3 V Dual-Loop, 50 Mbps to 3.3 Gbps

T

FEATURES

SFP/SFF and SFF-8472 MSA-compliant
SFP reference design available
50 Mbps to 3.3 Gbps operation
Multirate 155 Mbps to 3.3 Gbps operation
Dual-loop control of average power and extinction ratio
Typical rise/fall time 60 ps
Bias current range 2 mA to 100 mA
Modulation current range 5 mA to 90 mA
Laser fail alarm and automatic laser shutdown (ALS)
Bias and modulation current monitoring

3.3 V operation
4 mm × 4 mm LFCSP package
Voltage setpoint control
Resistor setpoint control

APPLICATIONS

Multirate OC3 to OC48-FEC SFP/SFF modules
1×/2×/4× Fibre channel SFP/SFF modules
LX-4 modules
DWDM/CWDM SFP modules
1GE SFP/SFF transceiver modules

Laser Diode Driver

ADN2870

GENERAL DESCRIPTION

The ADN2870 laser diode driver is designed for advanced SFP
and SFF modules, using SFF-8472 digital diagnostics. The device
features dual-loop control of the average power and extinction
ratio, which automatically compensates for variations in laser
characteristics over temperature and aging. The laser need only
be calibrated at 25°C, eliminating the need for expensive and
time consuming temperature calibration. The ADN2870 supports
single-rate operation from 50 Mbps to 3.3 Gbps or multirate
from 155 Mbps to 3.3 Gbps.

Average power and extinction ratio can be set with a voltage
provided by a microcontroller DAC or by a trimmable resistor.
The part provides bias and modulation current monitoring as
well as fail alarms and automatic laser shutdown. The device
interfaces easily with the ADI ADuC70xx family of micro­converters and with the ADN289x family of limiting amplifiers
to make a complete SFP/SFF transceiver solution. An SFP
reference design is available. The product is available in a space­saving 4 mm ×4 mm LFCSP package specified over the −40°C to
+85°C temperature range.

VCC

Tx_FAUL

Tx_FAIL

ADI

MICROCONTROLLER

DAC

ADC

DAC

1kΩ

1kΩ

VCC

GND

GND

MPD

PAVSET

PAVREF

RPAV

ERREF

ERSET

VCC

Figure 1. Application Diagram Showing Microcontroller Interface

Protected by US patent: US6414974

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.

GND

GND GND

VCC

L

R

IMODP

IBIAS

CCBIAS

VCC

LASER

DATAP

DATAN

ALSFAIL

CONTROL

IMOD

IBIAS

VCC

IMODN

100Ω

ADN2870

IBMON IMMON

470Ω1kΩ

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

PAVCAP

GND

ERCAP

GND

04510-001

www.analog.com

ADN2870

TABLE OF CONTENTS

Specifications..................................................................................... 3

SFP Timing Specifications............................................................... 5

Absolute Maximum Ratings............................................................ 6

ESD Caution.................................................................................. 6

Pin Configuration and Function Descriptions............................. 7

Typical Operating Characteristics.................................................. 8

Optical Waveforms Showing Multirate Performance Using

Low Cost Fabry Perot Tosa NEC NX7315UA

Optical Waveforms Showing Dual-Loop Performance Over

Temperature Using DFB Tosa SUMITOMO SLT2486

Performance Characteristics....................................................... 9

Theory of Operation ...................................................................... 11

Dual-Loop Control .................................................................... 11

Control......................................................................................... 12

.......................... 8

............ 8

REVISION HISTORY

Volt a ge S etp oint C al i brat ion ..................................................... 12

Resistor Setpoint Calibration.................................................... 14

IMPD Monitoring...................................................................... 14

Loop Bandwidth Selection ........................................................ 15

Power Consumption .................................................................. 15

Automatic Laser Shutdown (T X_Disable).............................. 15

Bias and Modulation Monitor Currents.................................. 15

Data Inputs .................................................................................. 15

Laser Diode Interfacing............................................................. 16

Alarms.......................................................................................... 17

Outline Dimensions....................................................................... 18

Ordering Guide .......................................................................... 18

8/04—Revision 0: Initial Version

Rev. 0 | Page 2 of 20

ADN2870

SPECIFICATIONS

VCC = 3.0 V to 3.6 V. All specifications T

Table 1.

Parameter Min Typ Max Unit Conditions/Comments

LASER BIAS CURRENT (IBIAS)

Output Current IBIAS 2 100 mA
Compliance Voltage 1.2 V
IBIAS when ALS is High 0.2 mA
CCBIAS Compliance Voltage 1.2 V

MODULATION CURRENT (IMODP, IMODN)

Output Current IMOD 5 90 mA
Compliance Voltage 1.5 V
IMOD when ALS is High 0.05 mA
Rise Time
Fall Time
Random Jitter
Deterministic Jitter
Pulse-Width Distortion

2, 3

2, 3

2, 3

2, 3

2, 3

AVERAGE POWER SET (PAVSET)

Pin Capacitance 80 pF
Voltage 1.1 1.2 1.35 V

Photodiode Monitor Current (Average Current) 50 1200 µA Resistor setpoint mode

EXTINCTION RATIO SET INPUT (ERSET)

Resistance Range 1.2 25 kΩ Resistor setpoint mode
Voltage 1.1 1.2 1.35 V Resistor setpoint mode

AVERAGE POWER REFERENCE VOLTAGE INPUT (PAVREF)

Voltage Range 0.12 1 V

Photodiode Monitor Current (Average Current) 120 1000 µA

EXTINCTION RATIO REFERENCE VOLTAGE INPUT (ERREF)

Voltage Range 0.1 1 V

DATA INPUTS (DATAP, DATAN)

4

V p-p (Differential) 0.4 2.4 V AC-coupled
Input Impedance (Single-Ended) 50 Ω

LOGIC INPUTS (ALS)

V

IH

V

IL

ALARM OUTPUT (FAIL)

V

OFF

V

ON

5

MIN

2

to T

,1 unless otherwise noted. Typical values as specified at 25°C.

MAX

CC

V

CC

V

60 104 ps
60 96 ps

0.8 1.1 ps rms
35 ps 20 mA < IMOD < 90 mA
30 ps 20 mA < IMOD < 90 mA

2 V

0.8 V

> 1.8 V

< 1.3 V

Voltage setpoint mode
(RPAV fixed at 1 kΩ)

Voltage setpoint mode
(RPAV fixed at 1 kΩ)

Voltage setpoint mode
(RERSET fixed at 1 kΩ)

Voltage required at FAIL for Ibias and
Imod to turn off when FAIL asserted

Voltage required at FAIL for Ibias and
Imod to stay on when FAIL asserted

Rev. 0 | Page 3 of 20

ADN2870

Parameter Min Typ Max Unit Conditions/Comments

IBMON, IMMON DIVISION RATIO

IBIAS/IBMON

IBIAS/IBMON

IBIAS/IBMON STABILITY

IMOD/IMMON 50 A/A

IBMON Compliance Voltage 0 1.3 V
SUPPLY

7

I

CC

VCC (w.r.t. GND)

1

Temperature range: –40°C to +85°C.

2

Measured into a 15 Ω load (22 Ω resistor in parallel with digital scope 50 Ω input) using a 11110000 pattern at 2.5 Gbps, shown in Figure 2.

3

Guaranteed by design and characterization. Not production tested.

4

When the voltage on DATAP is greater than the voltage on DATAN, the modulation current flows in the IMODP pin.

5

Guaranteed by design. Not production tested.

6

IBIAS/IBMON ratio stability is defined in SFF-8472 revision 9 over temperature and supply variation.

7

ICC min for power calculation in the Power Consumption section.

8

All VCC pins should be shorted together.

3

3

3, 6

85 100 115 A/A 11 mA < IBIAS < 50 mA
92 100 108 A/A 50 mA < IBIAS < 100 mA
±5 % 10 mA < IBIAS < 100 mA

30 mA When IBIAS = IMOD = 0

8

3.0 3.3 3.6 V

V

CCVCC

ADN2870

IMODP

22Ω

R

L

C

BIAS TEE

80kHz → 27GHz

Figure 2. High Speed Electrical Test Output Circuit

TO HIGH SPEED
DIGITAL
OSCILLOSCOPE
50Ω INPUT

04510-034

Rev. 0 | Page 4 of 20

ADN2870

SFP TIMING SPECIFICATIONS

Table 2.

Parameter Symbol Min Typ Max Unit Conditions/Comments

ALS Assert Time t_off 1 5 µs

ALS Negate Time

Time to Initialize, Including

Reset of FAIL

1

1

t_on 0.83 0.95 ms

t_init 25 275 ms From power-on or negation of FAIL using ALS.

FAIL Assert Time t_fault 100 µs Time to fault to FAIL on.
ALS to Reset time t_reset 5 µs Time TX_DISABLE must be held high to reset TX_FAULT.

1

Guaranteed by design and characterization. Not production tested.

V

SE

DATAP
DATAN

Time for the rising edge of ALS (TX_DISABLE) to when the bias
current falls below 10% of nominal.

Time for the falling edge of ALS to when the modulation current
rises above 90% of nominal.

SFP MODULE

VCC_Tx

1µH

3.3V

0.1µF 0.1µF 10µF

DATAP–DATAN

0V

Figure 3. Signal Level Definition

V p-p

DIFF

= 2× V

SFP HOST BOARD

SE

04510-002

Figure 4. Recommended SFP Supply

04510-003

Rev. 0 | Page 5 of 20

ADN2870

ABSOLUTE MAXIMUM RATINGS

TA = 25°C, unless otherwise noted.

Table 3.

Parameter Rating

VCC to GND 4. 2 V
IMODN, IMODP –0.3 V to +4.8 V
PAVCAP –0.3 V to +3.9 V
ERCAP –0.3 V to +3.9 V
PAVSET –0.3 V to +3.9 V
PAVREF –0.3 V to +3.9 V
ERREF –0.3 V to +3.9 V
IBIAS –0.3 V to +3.9 V
IBMON –0.3 V to +3.9 V
IMMON –0.3 V to +3.9 V
ALS –0.3 V to +3.9 V
CCBIAS –0.3 V to +3.9 V
RPAV –0.3 V to +3.9 V
ERSET –0.3 V to +3.9 V
FAIL –0.3 V to +3.9 V
DATAP, DATAN

(single-ended differential)

TEMPERATURE SPECIFICATIONS
Operating Temperature Range

Industrial

Storage Temperature Range –65°C to +150°C

Junction Temperature (TJ max) 150°C
LFCSP Package

Power Dissipation

θJA Thermal Impedance

θJCThermal Impedance 29.5°C/W
Lead Temperature (Soldering 10 s) 300°C

___________________

1

Power consumption equations are provided in the Power Consumption

section.

2

θJA is defined when part is soldered on a 4-layer board.

1

2

1.5 V

−40°C to +85°C

(TJ max – TA)/θJA W
30°C/W

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.

Rev. 0 | Page 6 of 20