
REV. 0
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otherwise under any patent or patent rights of Analog Devices.
a
Laser Dode Driver
wth 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 T T L/CMOS compatible.
T he 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.
T he 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.
T he AD9661A is offered in a 28-pin plastic SOIC for
operation over the commercial temperature range (0
°
C to
+70
°
C).
GE NE RAL DE SCRIPT ION
T he AD9661A is a highly integrated driver for laser diode appli-
cations such as printers and copiers. T he 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
FUNCT IONAL BLOCK DIAGRAM
PULSE2
DISABLE
CIRCUIT
DELAY
TTL
TTL
TTL
TTL
DISABLE
PULSE
DAC
C
GAIN
ANALOG
V
LEVEL SHIFT IN
+
V
REF
POWER
LEVEL
LEVEL
SHIFT OUT
LEVEL
SHIFT IN
50
REF
5pF
*13ns DELAY ON RISING
EDGE; 0ns ON FALLING
1:10
3–120mA
I
OUT
VOLT
REF
1:1
HOLD
V
REF
DIODE
+5V
PHOTO
V
REF
I
MONITOR
ANALOG
POWER
MONITOR
R
GAIN
GAIN
0–1.6V
CAL
SENSE IN
1.0V
8
I
MONITOR
V1
OUTPUT
LEVEL
SHIFT
CIRCUIT
AD9661A