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

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

a

Laser Diode Driver

with Light Power Control

AD9661A

© Analog Devices, Inc., 1995

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703

FEATURES

< 2 ns Rise/Fall Times

Output Current: 120 mA

Single +5 V Power Supply

Switching Rate: 200 MHz typ

Onboard Light Power Control Loop

APPLICATIONS

Laser Printers and Copiers

and fall times are 2 ns to complement printer applications that

use image enhancing techniques such as pulse width modula-

tion to achieve gray scale and resolution enhancement. Control

signals are TTL/CMOS compatible.

The driver output provides up to 120 mA of current into an

infrared N type laser, and the onboard disable circuit turns off

the output driver and returns the light power control loop to a

safe state.

The AD9661A can also be used in closed-loop applications in

which the output power level follows an analog POWER LEVEL

voltage input. By optimizing the external hold capacitor and

the photo detector, the loop can achieve bandwidths as high as

25 MHz.

The AD9661A is offered in a 28-pin plastic SOIC for

operation over the commercial temperature range (0

°C to

+70

°C).

GENERAL DESCRIPTION

The AD9661A is a highly integrated driver for laser diode appli-

cations such as printers and copiers. The AD9661A gets feed-

back from an external photo detector and includes an analog

feedback loop to allow users to set the power level of the laser,

and switch the laser on and off at up to 100 MHz. Output rise

FUNCTIONAL BLOCK DIAGRAM

PULSE2

DISABLE

CIRCUIT

DELAY

TTL

TTL

TTL

TTL

DISABLE

PULSE

DAC

ANALOG

POWER

LEVEL

LEVEL

SHIFT OUT

LEVEL

SHIFT IN

50

Ω

REF

5pF

*

*13ns DELAY ON RISING

EDGE; 0ns ON FALLING

1:10

3–120mA

VOLT

REF

1:1

HOLD

LASER

DIODE

+5V

PHOTO

DETECTOR

ANALOG

POWER

MONITOR

GAIN

0–1.6V

CAL

SENSE IN

1.0V

8

V1

OUTPUT

LEVEL

SHIFT

CIRCUIT

AD9661A