ANALOG DEVICES AD9668 Service Manual
4-Channel LVDS, Dual-Output,
*
FEATURES
Dual current-controlled output current sources
with 4 input channels
TTL-selectable output
Stable on-chip oscillators with independent frequency
and amplitude control
TTL- or LVDS-selectable write channel enables
TTL- or LVDS-selectable oscillator enable
150 mA minimum output current for Read Channel
275 mA minimum output current for Write Channel 1
170 mA minimum output current for Write Channel 2
150 mA minimum output current for Write Channel 3
Rise time/fall time of ≤0.8 ns
Low output overshoot
Low power consumption
Single 5 V power supply (±10%)
APPLICATIONS
DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM
supercombo drives
MO drives
Laser diode current switching
GENERAL DESCRIPTION
The AD9668 is a laser diode driver for high performance
CD-RW and DVD recordable drives. It includes four channels
for four different optical power levels; the Read Channel
generates a continuous output power level, whereas Channel 1,
Channel 2, and Channel 3 can be used as write channels that
can be controlled with either an LVDS or a TTL interface. The
OSCEN pin is also controlled by either an LVDS or a TTL
signal. All channels are summed at the selected LD output pin,
where Write Channel 1 can contribute at least 275 mA output
current, and Write Channel 2 and Write Channel 3 can contribute
at least 170 mA and 150 mA, respectively. The level of the output
current is set by an external resistor that converts an input voltage
into a current at the xSET pins.
An on-chip oscillator is provided to allow output current
modulation and to reduce laser mode hopping. Four external
resistors permit the setting of two different values for both
oscillator frequency and amplitude, one for each output. The
oscillator can output up to 100 mA p-p of current (push-pull
oscillator) with a frequency range of 200 MHz to 500 MHz.
Laser Diode Driver with Oscillator
AD9668
FUNCTIONAL BLOCK DIAGRAM
W3SET
W3EN
W3EN
W2SET
W2EN
W2EN
W1SET
W1EN
W1EN
RSET
RDEN
OSCEN
OSCEN
FADJ1 FADJ2
Figure 1. 4-Channel LVDS Laser Driver Block Diagram
W3EN*
W2EN*
W1EN*
ACTIVE LOW.
Figure 2. 4-Channel, LVDS, Laser-Driver Pin Configuration
For more information about the AD9668, contact
Analog Devices, Inc. at
WRITE
CHANNEL 3
WRITE
CHANNEL 2
WRITE
CHANNEL 1
READ CHANNEL
OSCILLATOR
1
2
W3EN
3
GND
4
GND
5
6
W2EN
7
8
W1EN
OUTPUT A
OUTPUT B
INSVDD OUTSEL VDD
AADJ2
AADJ1
VDD
OSCEN
OSCEN
OUTSELFADJ1
FADJ2
AADJ1
W2SET
W1SET
AADJ2
RSET
ENABLE
24
INS
23
VDD
22
LD1
21
LD1
20
GND
19
LD2
18
LD2
17
VDD
05444-055
32
31302928272625
AD9668
LFCSP
×
5mm
5mm
(Not to Scale)
9
10111213141516
VDD
GND
RDEN
W3SET
high_current_drivers.com@analog.com.
LD1
LD2
05444-001
Rev. Sp0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 © 2005 Analog Devices, Inc. All rights reserved.
AD9668
© 2005 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D05444F–0–7/05(Sp0)
Rev. Sp0 | Page 2 of 2
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