Analog Devices ADN2830 a Datasheet

Continuous Wave Laser

a

FEATURES
Bias Current Range 4 mA to 200 mA
Monitor Photodiode Current 50 A to 1200 A
Closed-Loop Control of Average Power
Laser FAIL and Laser DEGRADE Alarms
Automatic Laser Shutdown, ALS
Full Current Parameter Monitoring
5 V Operation
–40C to +85C Temperature Range
5 mm  5 mm 32-Lead LFCSP Package

APPLICATIONS
Fiber Optic Communication

Average Power Controller

ADN2830

GENERAL DESCRIPTION

The ADN2830 provides closed-loop control of the average
optical power of a continuous wave (CW) laser diode (LD)
after initial factory setup. The control loop adjusts the laser
IBIAS to maintain a constant back facet monitor photodiode
(MPD) current and thus a constant laser optical power. The
external PSET resistor is adjusted during factory setup to set
the desired optical power. R
is the MPD current corresponding to the desired optical power.
Programmable alarms are provided for laser fail (end of life)
and laser degrade (impending fail).

To provide monitoring of the MPD current, the MPD can be
connected to the IMPD pin. In this case, the MPD current is
mirrored to the IMPDMON pin to provide a monitor and
internally to the PSET pin to close the control loop.

By closing the feedback using IBMON rather than an MPD
connected to PSET, the device is configured to control a constant
current in the laser rather than a constant optical output power.

is set at 1.23/IAV, where I

PSET

AV

R

MPD

PSET

V

GND

CC

FUNCTIONAL BLOCK DIAGRAM

IBMON IMPDMON ALS FAI L DEGRADE

IMPD

GND

PSET

GND

PAV CAP

CONTROL

MODE

V

GND

CC

IBIAS

ASET

LD

GND

V

CC

R

ASET

REV. AREV. A

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. 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 companies.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2003 Analog Devices, Inc. All rights reserved.

ADN2830–SPECIFICATIONS

(VCC = 5 V  10%. All specifications T
Typical values as specified at 25C.)

MIN

to T

, unless otherwise noted1.

MAX

Parameter Min Typ Max Unit Conditions/Comments

LASER BIAS (BIAS)

Output Current IBIAS 4 200 mA
Compliance Voltage 1.2

V

CC

V
IBIAS during ALS 40 µA
ALS Response Time 10 µs

MONITOR PD (IMPD)

Current 50 1200 µA
Input Voltage 1.6 V

POWER SET INPUT (PSET)

Capacitance 80 pF
Input Current 50 1200 µA
Voltage 1.15 1.23 1.35 V

ALARM SET (ASET)

Allowable Resistance Range 1.2 13 kΩ
Voltage 1.15 1.23 1.35 V
Hysteresis 5 %

LOGIC INPUTS (ALS, MODE)

V

IH

V

IL

2.4 V

0.8 V

ALARM OUTPUTS (Internal 30 kΩ Pull-Up)

V

OH

V

OL

2.4 V

0.4 V

IBMON IMPDMON

IBMON, Division Ratio 100 A/A
IMPDMON Division Ratio 1 A/A
Compliance Voltage 0 VCC – 1.2 V

SUPPLY

2

I

CC

V

CC

NOTES

1

Temperature range: –40°C to +85°C.

2

ICC for power calculation is the typical ICC given.

Specifications subject to change without notice.

4.5 5.0 5.5 V

25 mA IBIAS = 0

–2–

REV. A

ADN2830

ABSOLUTE MAXIMUM RATINGS

(TA = 25°C, unless otherwise noted.)

1

VCCto GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V

Digital Inputs (ALS, Mode) . . . . . . . . .–0.3 V to V

+ 0.3 V

CC

Operating Temperature Range

Industrial . . . . . . . . . . . . . . . . . . . . . . . . . . –40°Cto+85°C

NOTES

1

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.

2

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

Storage Temperature Range . . . . . . . . . . –65°Cto+150°C

Junction Temperature (T

Max ) . . . . . . . . . . . . . . . . . 150°C

J

θJA Thermal Impedance2 . . . . . . . . . . . . . . . . . . . . 32°C/W

32-Lead LFCSP Package,

Power Dissipation . . . . . . . . . . . . . . (T

Max – TA)/θJAmW

J

Lead Temperature (Soldering 10 sec) . . . . . . . . . . . . . . 300°C

ORDERING GUIDE

Model Temperature Range Package Description

ADN2830ACP32 –40°C to +85°C 32-Lead LFCSP
ADN2830ACP32-REEL7 –40°C to +85°C 32-Lead LFCSP
ADN2830ACP32-REEL –40°C to +85°C 32-Lead LFCSP

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
the ADN2830 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.

WARNING!

ESD SENSITIVE DEVICE

REV. A

–3–

ADN2830

PIN CONFIGURATION

3

CC

24 IBMON

23 IBMON

22 GND3

21 V

20 ALS

19 FAIL

18 DEGRADE

17 MODE

25

2

V

CC

NC 26
GND2 27
IBIAS 28
GND2 29
GND2 30
IBIAS 31

NC 32

NC = NO CONNECT

ADN2830

TOP VIEW

PIN 1
INDICATOR

NC 3

GND 1

ASET 2

IMPD 5

PSET 4

PIN FUNCTION DESCRIPTIONS

Pin No. Mnemonic Function

1GND Supply Ground
2 ASET Alarm Current Threshold Set Pin
3NCNo Connect
4 PSET Average Optical Power Set Pin
5 IMPD Monitor Photodiode Input
6IMPDMON Mirrored Current from Monitor Photodiode—Current Source
7 GND4 Supply Ground
8V

4 Supply Voltage

CC

9 PAVCAP Average Power Loop Capacitor
10 PAVCAP Average Power Loop Capacitor
11 V
12 V

1 Supply Voltage

CC

5 Supply Voltage

CC

13 NC No Connect
14 GND1 Supply Ground
15 NC No Connect
16 NC No Connect
17 MODE Mode Select: Tied to ALS = Standalone, High = Parallel Current Booster
18 DEGRADE DEGRADE Alarm Output
19 FAIL FAIL Alarm Output
20 ALS Automatic Laser Shutdown
21 V

3 Supply Voltage

CC

22 GND3 Supply Ground
23 IBMON Bias Current Monitor Output—Current Source
24 IBMON Bias Current Monitor Output—Current Source
25 V

2 Supply Voltage

CC

26 NC No Connect
27 GND2 Supply Ground
28 IBIAS Laser Diode Bias Current
29 GND2 Supply Ground
30 GND2 Supply Ground
31 IBIAS Laser Diode Bias Current
32 NC No Connect

8

4

CC

V

GND4 7

IMPDMON 6

16 NC
15 NC
14 GND1
13 NC
12 V

5

CC

11

V

1

CC

10 PAVCAP
9 PAVCAP

–4–

REV. A

ADN2830

GENERAL

Laser diodes have current-in to light-out transfer functions as
shown in Figure 1. Two key characteristics of this transfer func­tion are the threshold current, I

, and slope in the linear region

TH

beyond the threshold current, referred to as slope efficiency (LI).

P

OPTICAL POWER

AV

⌬P

⌬P

LI =

⌬I

I

TH

⌬ I

CURRENT

Figure 1. Laser Transfer Function

CONTROL

A monitor photodiode (MPD) is required to control the laser
diode. The MPD current is fed into the ADN2830 to control
the power, continuously adjusting the bias current in response
to the laser’s changing threshold current and light to current
(LI) slope (slope efficiency).

The ADN2830 uses automatic power control (APC) to maintain
a constant power over time and temperature.

The average power is controlled by the R

PSET

resistor
connected between the PSET pin and ground. The PSET pin
is kept 1.23 V above GND. For an initial setup, the R

PSET

resis-

tor can be calculated using the following formula.

PSET

123.

=

I

AV

where I

AV

Note the I

R

is average MPD current.

will change from device to device. It is not

PSET

V

required to know exact values for LI and MPD optical coupling.

LOOP BANDWIDTH SELECTION

Capacitor values greater than 22 nF are used to set the actual
loop bandwidth. This capacitor is placed between the PAVCAP
pin and ground. It is important that the capacitor is a low leak­age multilayer ceramic with an insulation resistance greater than
100 GΩ or a time constant of 1000 sec, whichever is less.

ALARMS

The ADN2830 has two active high alarms, DEGRADE and
FAIL. A resistor between ground and the ASET pin is used to
set the current at which these alarms are raised. The current
through the ASET resistor is a ratio of (N ⫻ 200):1 to the FAIL
alarm threshold (N is the number of ADN2830s in parallel).
The DEGRADE alarm will be raised at 90% of this level.

Example:

ImANI mA

==∴=50 1 45,

FAIL DEGRADE

I

*R

I

BIASTRIP

=

ASET

ASET

×

20050200

N

V

123 123

..

== =

IA

ASET

mA

==µ

250

250

492

.µΩ

A

k

The laser degrade alarm, DEGRADE, gives a warning of imminent
laser failure if the laser diode degrades further or environmental condi­tions continue to stress the laser diode, e.g., increasing temperature.

The laser fail alarm, FAIL, is activated when:

•

The ASET threshold is reached.

•

The ALS pin is set high. This shuts off the modulation and
bias currents to the laser diode, resulting in the MPD current
dropping to zero.

DEGRADE will only be raised when the bias current exceeds
90% of the ASET current.

MONITOR CURRENTS

IBMON and IMPDMON are current controlled current sources
from V

. They mirror the bias and MPD current for increased

CC

monitoring functionality. An external resistor to GND gives a
voltage proportional to the current monitored. If the IMPDMON
function is not used, the IMPD pin must be grounded and the
monitor photodiode must be tied directly to the PSET pin.

AUTOMATIC LASER SHUTDOWN

When ALS is logic high, the bias current is turned off. Correct
operation of ALS can be confirmed by the fail alarm being
raised when ALS is asserted. Note that this is the only time
DEGRADE will be low while FAIL is high.

MODE

The MODE feature on the ADN2830 allows the user to operate
more than one ADN2830 in parallel current boosting mode to
achieve up to N ⫻ 200 mA of bias current (N is the number of
ADN2830s in parallel). When using parallel boosting mode,
device is run as the master, the other as the slave. The

one

MODE
pin on the master is tied to ALS and the MODE pin on the
slave is tied high (see Figure 3 for reference circuit).

ALARM INTERFACES

The FAIL and DEGRADE outputs have an internal 30 kΩ
pull-up resistor that is used to pull the digital high value to V

CC.

However, the alarm output may be overdriven with an external
resistor allowing the alarm interfacing to non-V
Non-V

alarm output levels must be below the VCC used for

CC

levels.

CC

the ADN2830.

*The smallest value for R

maximum of N ⫻ 200 mA.

REV. A

is 1.2 kΩ, as this corresponds to the IBIAS

ASET

–5–

ADN2830

POWER CONSUMPTION

The ADN2830 die temperature must be kept below 125°C.
The exposed paddle should be connected in such a manner that
it is at the same potential as the ADN2830 ground pins. Power
consumption can be calculated using the following formulas.

TT P

=+×θ

DIE AMBIENT A

II

=

CC CCMIN

PV I IBIAS V

=×+ ×

CC CC BIAS PIN

()

MPD

J

_

V

CC

LD

32

NC = NO CONNECT

V

24

IBMON

VCC2

NC

GND2

IBIAS

GND2

GND2

IBIAS

NC

GND

18

3

CC

V

GND3

IBMON

ADN2830

ASETNCPSET

CC

ALS

IMPD

FAIL

DEGRADE

IMPDMON

GND4

MODE

NC

NC

GND1

NC

VCC5

VCC1

PAV CAP

PAV CAP

4

CC

V

FAIL

DEGRADE

16

1F

V

100nF 10F

PLACE 100nF CAP
CLOSE TO PIN 8

CC

GND

Figure 2. Test Circuit, Standalone Mode, IMPD Input Not Used

–6–

REV. A

V

CC

MPD

NC = NO CONNECT

ADN2830

V

CC

FAIL

DEGRADE

LD

24

IBMON

VCC2

NC

GND2

IBIAS

GND2

GND2

IBIAS

NC

32

GND

18

3

CC

V

GND3

IBMON

ADN2830

ASETNCPSET

ALS

IMPD

FAIL

DEGRADE

IMPDMON

GND4

MODE

NC

NC

GND1

NC

VCC5

VCC1

PAV CAP

PAV CAP

4

CC

V

16

100nF

PLACE 100nF CAP
CLOSE TO PIN 8

V

CC

100nF 10F

GND

NC = NO CONNECT

24

IBMON

VCC2

NC

GND2

IBIAS

GND2

GND2

IBIAS

NC

32

GND

18

3

CC

V

GND3

IBMON

ADN2830

ASETNCPSET

ALS

IMPD

FAIL

DEGRADE

IMPDMON

GND4

MODE

NC

NC

GND1

NC

VCC5

VCC1

PAV CAP

PAV CAP

4

CC

V

16

Figure 3. Test Circuit, Second ADN2830 Used in Parallel Current Boosting Mode to Achieve 400 mA Max IBIAS

REV. A

–7–

ADN2830

V

CC

FAIL

DEGRADE

V

CC

MPD

NOTES

1.FOR DIGITAL CONTROL, REPLACE R
ADN2850 10-BIT RESOLUTION, 35 ppm/C TC, EEPROM; AD5242 8-BIT RESOLUTION, 30 ppm/C TC.

2.TOTAL CURRENT TO LASER = IBIAS + IBIAS  R1/R2.

3.FOR BEST ACCURACY, SIZE R1 TO HAVE A MAXIMUM VOLTAGE DROP ACROSS IT WITHIN THE HEADROOM
CONSTRAINTS.

4.FOR 250 mA EXTRA IBIAS (450 mA TOTAL) FROM AMP1, USE AD8591 AMPLIFIER. AMP1 IS THE OPERATIONAL AMPLIFIER
SHOWN IN THIS FIGURE.

5.FOR 350 mA EXTRA IBIAS (550 mA TOTAL) FROM AMP1, USE ANALOG DEVICES’ SSM2211 AMPLIFIER. AMP1 IS THE
OPERATIONAL AMPLIFIER SHOWN IN THIS FIGURE.

V

CC

LD

R1R2

32

NC = NO CONNECT

24

IBMON

VCC2

NC

GND2

IBIAS

GND2

GND2

IBIAS

NC

GND

18

WITH A DIGITAL POTENTIOMETER FROM ANALOG DEVICES:

PSET

3

CC

V

GND3

IBMON

ADN2830

ASETNCPSET

ALS

IMPD

FAIL

DEGRADE

IMPDMON

GND4

MODE

NC

NC

GND1

NC

VCC5

VCC1

PAV CAP

PAV CAP

4

CC

V

16

100nF 10F

V

CC

GND

PLACE 100nF CAP
CLOSE TO PIN 8

CURRENT GAIN =

V

CC

R2

LD

Figure 4. The ADN2830 Configured with Current Multiplier

V

CC

FAIL

DEGRADE

R1
R2

R1

V

CC

AD820

V

CC

MPD

NC = NO CONNECT

V

CC

24

IBMON

VCC2

NC

GND2

IBIAS

GND2

GND2

IBIAS

NC

32

GND

18

3

CC

V

GND3

IBMON

ADN2830

ASETNCPSET

ALS

IMPD

FAIL

DEGRADE

IMPDMON

GND4

MODE

NC

NC

GND1

NC

VCC5

VCC1

PAV CAP

PAV CAP

4

CC

V

16

100nF 10F

PLACE 100nF CAP
CLOSE TO PIN 8

V

CC

GND

Figure 5. The ADN2830 Configured as Average Power Controller (Bias Current Sourced)

–8–

REV. A

V

CC

LD

VCC2

NC

GND2

IBIAS

GND2

GND2

IBIAS

NC

32

NC = NO CONNECT

V

CC

FAIL

DEGRADE

24

IBMON

GND

18

3

CC

V

GND3

IBMON

ADN2830

ASETNCPSET

ALS

IMPD

FAIL

DEGRADE

IMPDMON

GND4

MODE

NC

NC

GND1

NC

VCC5

V

CC

PAV CAP

PAV CAP

4

CC

V

16

1

V

CC

100nF 10F

PLACE 100nF CAP
CLOSE TO PIN 8

ADN2830

GND

Figure 6. The ADN2830 Configured as a Controlled Current

Source by Feeding Back the Bias Monitor Current to R

PSET

REV. A

–9–

ADN2830

OUTLINE DIMENSIONS

32-Lead Frame Chip Scale Package [LFCSP]

(CP-32)

Dimensions shown in millimeters

PIN 1

INDICATOR

1.00

0.90

0.80

12 MAX

SEATING
PLANE

5.00

BSC SQ

TOP

VIEW

0.80 MAX

0.65 NOM

0.30

0.23

0.18

COMPLIANT TO JEDEC STANDARDS MO-220-VHHD-2

4.75

BSC SQ

0.20 REF

0.05 MAX

0.02 NOM

0.60 MAX

0.50
BSC

0.50

0.40

0.30

COPLANARITY

0.08

0.60 MAX

25

24

17

16

BOTTOM

VIEW

32

9

1

8

3.50 REF

PIN 1
INDICATOR

3.25
SQ

3.10

2.95

0.25 MIN

Revision History

Location Page

6/03—Data Sheet changed from REV. 0 to REV. A.

Changes to ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

–10–

REV. A

–11–

C03020–0–6/03(A)

–12–