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PDF AD9665 Data sheet ( Hoja de datos )
| Número de pieza | AD9665 | |
| Descripción | Laser Diode Driver | |
| Fabricantes | Analog Devices | |
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Data Sheet
4-Channel, LVDS, Dual-Output,
Laser Diode Driver with Oscillator
AD9665
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 negative logic
Independent TTL oscillator enables positive logic
170 mA minimum output current for the read channel
510 mA minimum output current for Write Channel 1
330 mA minimum output current for Write Channel 2
165 mA minimum output current for Write Channel 3
950 mA typical total output current
Typical rise time/fall time of 0.8 ns
Low power consumption
Single 5 V power supply (±10%)
APPLICATIONS
DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM
supercombo drives
Magneto-optical (MO) drives
Laser diode current switching
OTDR laser drivers
GENERAL DESCRIPTION
The AD9665 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 an LVDS or TTL interface. The WxDIS and
RDIS pins are active low logic. The OSCEN pin is controlled by
an active high TTL signal. All active channels are summed at
the output where Write Channel 1 can contribute at least
325 mA output current, and Write Channel 2 and Write
Channel 3 can contribute at least 250 mA and 150 mA,
respectively. The level of the output current is set by an
external resistor, which converts this voltage into a current
at the WxSET pin.
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 distinct values for the
frequency and swing of the oscillator. 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.
W3SET
W3DIS
W3DISN
FUNCTIONAL BLOCK DIAGRAM
WRITE
CHANNEL 3
W2SET
W2DIS
W2DISN
WRITE
CHANNEL 2
OUTPUT A LD1
W1SET
W1DIS
W1DISN
RSET
RDIS
WRITE
CHANNEL 1
READ CHANNEL
OUTPUT B LD2
OSCEN
OSCILLATOR
ENABLE
INS OUTSEL
FADJ1 FADJ2 AADJ1 AADJ2
Figure 1. 4-Channel, LVDS, Laser Driver Block Diagram
W3DISN 1
W3DIS* 2
GND 3
GND 4
W2DISN 5
W2DIS* 6
W1DISN 7
W1DIS* 8
AD9665
LFCSP
5mm × 5mm
(Not to Scale)
24 INS
23 VDD
22 LD1
21 LD1
20 GND
19 LD2
18 LD2
17 VDD
*TTL ACTIVE LOW
NOTES
1. DNC = DO NOT CONNECT. LEAVE THIS PIN
FLOATING WITH NO EXTERNAL CONNECTION.
2. WHEN PULLING A HIGH CURRENT, ATTACH
HEAT SINK ON THE EXPOSED PAD.
Figure 2. 4-Channel, LVDS, Laser Driver Pin Configuration, See Table 3
Rev. F
Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor other
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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2010–2015 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
AD9665
Data Sheet
Parameter
Disable Time Oscillator
Enable Time Oscillator
LOGIC SPECIFICATIONS
INS = 1 (LVDS Mode)
Minimum Differential Input Voltage
Maximum Differential Input Voltage
Valid Input Voltage
OUTEN
Logic HI Threshold
Logic LO Threshold
SUPPLY CURRENT9
INS = 1 (LVDS Mode)
Power Down
Inputs Disabled, Read Enabled
Inputs Disabled, Oscillator Enabled
Read Mode, Oscillator Enabled11
IOUT = 50 mA
Write Mode11
IOUT = 150 mA (50 mA Write
Channel 1, Write Channel 2,
Write Channel 3)
INS = 0 (TTL Mode)
Power-Down
Inputs Disabled, Read Enabled
Inputs Disabled, Oscillator Enabled
Read Mode, Oscillator Enabled11
IOUT = 50 mA
Write Mode11
IOUT = 150 mA (50 mA Write
Channel 1, Write Channel 2,
Write Channel 3)
OPERATING CONDITIONS
Supply Voltage Range
Operating Temperature Range
Conditions
OSCEN 50% H-L to IOUT at 50% of final value, OSCEN = 1
OSCEN 50% L-H to IOUT at 50% of final value, OSCEN = 1
Min Typ Max Unit
2 ns
4 ns
Magnitude
Magnitude
Relative to GND
100
0
Temperature stabilized
Temperature stabilized
ENABLE OSCEN RDIS
W1DIS10
W2DIS10
W3DIS10
2.0
0 0 11 1 1
1 0 01 1 1
1 1 11 1 1
1 1 01 1 1
8.6
26
46
54
1 0 10 0 0
49
mV
600 mV
2.4 V
V
0.8 V
mA
mA
mA
mA
mA
0 0 11 1 1
1 0 01 1 1
1 1 11 1 1
1 1 01 1 1
1 0 10 0 0
9.5 mA
23 mA
43 mA
51 mA
43 mA
4.5 5.5 V
−25 +85 °C
1 Output linearity, offset current, and gain are calculated using the best-fit method at 30 mA, 60 mA, and 90 mA. The transfer function is IOUT = (IIN × GAIN) + IOS.
2 Output linearity, offset current, and gain are calculated using the best-fit method at 90 mA, 120 mA, and 150 mA. The transfer function is IOUT = (IIN × GAIN) + IOS.
3 Output linearity, offset current, and gain are calculated using the best-fit method at 60 mA, 90 mA, and 120 mA. The transfer function is IOUT = (IIN × GAIN) + IOS.
4 Output linearity is calculated using the best-fit method, which is calculated at 90 mA, 120 mA, and 150 mA, extrapolated to IIN = 2 mA.
5 Measured electrically from 10% to 90% of final value. Sharp Diode—GH06550B2B (see Figure 14).
6 Measured electrically from 10% to 90% of final value. Mitsubishi Diode—ML101J26. RL = 0.66 Ω (see Figure 14).
7 Measured electrically from 90% to 10% of final value. Sharp Diode—GH06550B2B (see Figure 14).
8 Measured electrically from 90% to 10% of final value. Mitsubishi Diode—ML101J26. RL = 0.66 Ω (see Figure 14).
9 See the Shutdown Supply Current Variation section for more information.
10 WxDIS = 0 means channel is off regardless of mode: TTL or LVDS (see Table 3). WxDIS = 1 means channel is on regardless of mode: TTL or LVDS (see Table 3).
11 The value specified does not include the output current.
Rev. F | Page 4 of 16
5 Page 
AD9665
is highly dependent on the board layout, material, and heat
sink. The user must consider these conditions carefully.
Some of the circuitry of the AD9665 can be used to monitor the
internal junction temperature.
The AD9665 uses a combination of diodes and transistors to
protect it from electrostatic discharge (ESD). All input pins have
a diode between them and ground, with the anode connected to
ground and the cathode connected to the particular input pin.
The base-emitter junction of a PNP transistor is used for ESD
protection for each pin to VDD. The collector is electrically
connected to the substrate of the die (see Figure 16). The base-
emitter junction of this transistor can be used to monitor the
internal die temperature of the IC.
Using a 10 V source at the enable pin to forward-bias the base-
emitter junction and a 1 MΩ resistor to limit the current, a
2-point measurement can be used to calculate the junction
temperature of the IC. Because the enable pin (ENABLE) needs
to be high for normal operation, the AD9665 can be operated
normally with the 10 V applied through the 1 MΩ resistor.
For this experiment, V1 and V2 were measured between the
ENABLE pin (Pin 16) and the closest VDD pin (Pin 17).
IDD AD9665
VDD
5V
–
V1, V2
+
1M
IBE
RS
ENABLE
10V
GND
Figure 16. Junction Temperature Measurement Circuit
The most important aspect of measuring junction temperature
on the AD9665 is that only one variable in the system is
changed at a time. In this case, the only variable is the amount
of power being dissipated by the AD9665. Therefore, the
ambient temperature should be held constant. For example, to
measure the junction temperature of the AD9665 while
operating at 60°C ambient, the ambient temperature must be
held constant for both the initial measurement, V1, and the
final measurement, V2. This is true because of the relationship
between temperature and VBE. For the process with which the
AD9665 is fabricated, the change in VBE (ΔVBE) is related to the
die temperature by −1.9 mV/°C (note the negative coefficient).
Therefore, die temperature is directly related to ambient
temperature and the power dissipated.
Data Sheet
While the power to the AD9665 is disconnected, the AD9665
should be allowed to reach thermal equilibrium (at the desired
ambient temperature). With all channels turned off such that
IOUT = 0 mA, measure V1 as shown in Figure 16 (note the
polarity).
The second point of the 2-point measurement is obtained when
the AD9665 is operated under load, for example, while driving a
laser. Before taking the measurement, the AD9665 must be
allowed adequate time to reach a thermal equilibrium.
As seen in Figure 16, the AD9665 has a finite parasitic resistance
(RS) between VDD (Pin 17) and the base of the PNP transistor.
This resistance is typically 120 mΩ. Because the goal of the
experiment is to measure ΔVBE of the transistor, the voltage
drop across this resistance must be taken into account to get an
accurate representation of the actual ΔVBE. This voltage drop
varies depending on the output current of the AD9665
operating under load. Therefore, the actual supply current (IDD)
must be measured for each measurement.
VDROP = IDD × RS
So the resulting ΔVBE can be found as
ΔVBE = (V2 + VDROP2) − (V1 + VDROP1)
For increasing temperature, this result should be negative.
From ΔVBE, the final junction temperature is determined by
TJ
TA
ΔVBE
1.9 mV/C
From the resulting temperature rise in addition to the measured
power dissipation, the thermal resistance from the junction to
ambient can be calculated as
PD = VDD × IDD − VLOAD × ILOAD
θJA
TJ TA
PD
Rev. F | Page 10 of 16
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet AD9665.PDF ] | |
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