REV. 0

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a

AD9561

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

Tel: 617/329-4700

World Wide Web Site: http://www.analog.com

Fax: 617/326-8703

© Analog Devices, Inc., 1996

Pulse Width Modulator

FUNCTIONAL BLOCK DIAGRAM

RAMP

RAMP

CLOCK

CAL IN

8-BIT

DATA

SEM/DEM

LEM/TEM

RETRACE

REF

DAC

OUTPUT

LOGIC

PWM

OUT

CAL

DAC

INTERNAL

TIMING

L

A

T

C

H

L

A

T

C

H

AD9561

CAL

OUT

CAL

OUT

FEATURES

60 MHz Pulse Rate

8-Bit Resolution

Center, Left or Right Justify

Low Power: 700 mW typical

Minimum Pulse Width: <5 ns

Maximum PW: 100 % Full-scale

APPLICATIONS

Laser Printers

Digital Copiers

Color Copiers

GENERAL DESCRIPTION

The AD9561 is a second generation high speed, digitally

programmable pulse width modulator (PWM). Output pulse

width is proportional to an 8-bit DATA input value. Two

additional control inputs determine if the pulse is placed at the

beginning, middle or end of the clock period. Pulse width and

placement can be changed every clock cycle up to 60 MHz.

Pulse width modulation is a well proven method for controlling

gray scale and resolution enhancement in scanning laser print

engines. Modulating pulse width provides the most cost

effective method for continuous tone reproduction and resolu-

tion enhancement in low-to-moderate cost scanning electro-

photographic systems.

The AD9561 uses precision analog circuits to control dot size

so that near-photographic quality images are practical without

the high frequency clock signals required by all digital approaches.

The AD9561 has improved features and performance over its

predecessor, the AD9560. An improved ramp topology enables

control of pulse width through 100% of the dot clock period as

opposed to 95% for the AD9560. This enables smooth transi-

tion across dot boundaries for line screen applications.

Additionally, input data setup and hold time are symmetrical at

2 ns each, simplifying interface to the system bus.

Finally, chip design and pinout are optimized to decrease

sensitivity of analog circuits to digital coupling. (See layout

section for detailed recommendations for optimum results.)

Inputs are TTL or CMOS compatible, and outputs are CMOS

compatible. The AD9561JR is packaged in a 28-lead plastic

SOIC. It is rated over the commercial temperature range, 0

°C

to +70

°C.

HIGHLIGHTS

1. 60 MHz native printer clock rate.

2. Single +5 V power supply.

3. On-chip Autocalibration.

4. Pulse placement flexibility.

5. High resolution: 256 pulse widths.