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Details, datasheet, quote on part number:AD9660
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Datasheet text preview:
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FEATURES 1.5 ns Rise/2.0 ns Fall Times Output Current: 180 mA @ 3 V, 200 mA @ 2.5 V Bias Current: 90 mA @ 3 V Modulation Current: 60 mA @ 3 V Offset Current: 30 mA @ 3 V Single +5 V Power Supply Switching Rate: 200 MHz Onboard Light Power Control Loops APPLICATIONS Laser Printers and Copiers Optical Disk Drives FO Datacomm
200 MHz Laser Diode Driver with Light Power Control AD9660
FUNCTIONAL BLOCK DIAGRAM
WRITE PULSE WRITE CALIBRATE WRITE LEVEL T/H V:1 OUTPUT DRIVER
OUTPUT LASER DIODE
TRANSIMPEDANCE AMPLIFIER
SENSE INPUT PHOTO DETECTOR DIODE
BIAS LEVEL BIAS CAL
BIAS T/H
V:1
OUTPUT DRIVER
AD9660
GENERAL DESCRIPTION
The AD9660 is a highly integrated driver for laser diode applications such as optical disk drives, printers, and copiers. The AD9660 gets feedback from an external photo detector and includes two analog feedback loops to allow users to set "bias" and "write" (for optical disk drives) power levels of the laser, and switch between the two power levels at up to 200 MHz. Output rise and fall times are typically 1.5 ns and 2.0 ns to complement printer applications that use image enhancing techniques such as pulse width modulation to achieve gray scale, and allow disk drive applications to improve density and take advantage of pulsed write formats. Control signals are TTL/ CMOS compatible.
The driver output provides up to 180 mA of current @ 3 V, 90 mA of BIAS current, 60 mA of modulation current, and 30 mA of offset current. The onboard disable circuit turns off the output drivers and returns the light power control loops to a safe state. The AD9660 can also be used in closed loop applications in which the output power level follows an analog WRITE LEVEL voltage input. By optimizing the external hold capacitor, and the photo detector, the write loop can achieve bandwidths as high as 25 MHz. The AD9660 is offered in a 28-pin plastic SOIC for operation over the commercial temperature range (0°C to +70°C).
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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. © 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
AD9660SPECIFICATIONS as positive.)
Parameter ANALOG INPUTS (WRITE LEVEL, BIAS LEVEL) Input Voltage Range Input Bias Current Analog Bandwidth OUTPUTS Maximum Output Current, IOUT IOUT Bias Current, IBIAS Modulation Current, IMODULATION Offset Current, IOFFSET Output Compliance Range Idle Current SWITCHING PERFORMANCE Maximum Pulse Rate Output Propagation Delay (tPD), Rising1 Output Propagation Delay (tPD), Falling1 Output Current Rise Time2 Output Current Fall Time3 WRITE CAL Aperture Delay4 Disable Time5 HOLD NODES (WRITE HOLD, BIAS HOLD) Input Bias Current Input Voltage Range Minimum External Hold Cap TTL INPUTS6 Logic "1" Voltage Logic "1" Voltage Logic "0" Voltage Logic "0" Voltage Logic "1" Current Logic "0" Current BANDGAP REFERENCE Output Voltage VREF Temperature Coefficient Output Current SENSE IN Current Gain Voltage Input Resistance POWER SUPPLY (DISABLE = HIGH) +VS Voltage +VS Current Power Dissipation OFFSET CURRENT OFFSET SET Voltage Test Level Temp IV I V I I I I I I I Full + 2 5° C Full + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C
(+VS = +5 V, Temperature = +25°C unless otherwise noted. Sourced currents defined
AD9660KR Typ Max
Min
Units
Conditions
V REF 50 25 200 180 90 60 30 0 3
VREF + 1.6 +50
V µA MHz mA mA mA mA mA V mA
External Hold Cap = 20 pF VOUT = 2.5 V VOUT = 3.0 V VOUT = 3.0 V VOUT = 3.0 V VOUT = 3.0 V WRITE PULSE = LOW, DISABLE = HIGH 3 dB Reduction in IOUT
3.0 13
IV IV IV IV IV V V
+25°C Full Full Full Full + 2 5° C + 2 5° C
200 1.6 1.6 1.1 1.4
250 1.5 2.0 13 5 3.0 2.5 1.7 2.8
MHz ns ns ns ns ns ns
I IV V I IV I IV I I I V V V I V I I I I
+ 2 5° C Full Full + 2 5° C Full +25°C Full + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C + 2 5° C
200 V REF 20 2.0 2.0 10 1.5 1.55 0.5 1.85 4.0 <150 5.00 110 550 1.4 20
200 nA VREF + 1.6 V pF V V V V µA mA V m V /° C mA mA/mA V V mA mW V
VHOLD = 2.5 V Open Loop Application Only
0.8 0.8 10
DISABLE = LOW While Other TTL Inputs Are Tested
1.75 0.2
1.90 1.0
3.7
4.3
IMONITOR = 2 mA
4.75 75
5.25 150
DISABLE = HIGH
1.1
1.7
IMONITOR = 4.0 mA
NOTES 1 Propagation delay measured from the 50% of the rising/falling transition of WRITE PULSE to 50% point of the rising/falling edge of the output modulation current. 2 Rise time measured between the 10% and 90% points of the rising transition of the modulation current. 3 Fall time measured between the 10% and 90% points of the falling transition of the modulation current. 4 Aperture Delay is measured from the 50% point of the rising edge of WRITE PULSE to the time when the output modulation begins to recalibrate, WRITE CAL is held during this test. 5 Disable Time is measured from the 50% point of the rising edge of DISABLE to the 50% point of the falling transition of the output current. Fall time during disable is similar to fall time during normal operation. 6 WRITE PULSE, WRITE CAL, BIAS CAL, OFFSET PULSE are TTL compatible inputs. Specifications subject to change without notice.
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AD9660
ABSOLUTE MAXIMUM RATINGS 1
+VS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6 V VREF Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 mA WRITE LEVEL, BIAS LEVEL . . . . . . . . . . . . . 0.5 V to +VS TTL INPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 V to +VS Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 mA Operating Temperature AD9660KR . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C Storage Temperature . . . . . . . . . . . . . . . . . . 65°C to +150°C Maximum Junction Temperature2 . . . . . . . . . . . . . . . . +150°C Lead Soldering Temp (10 sec) . . . . . . . . . . . . . . . . . . . +300°C
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EXPLANATION OF TEST LEVELS Test Level
Absolute maximum ratings are limiting values, to be applied individually, and beyond which the serviceability of the circuit may be impaired. Functional operability under any of these conditions is not necessarily implied. Exposure of absolute maximum rating conditions for extended periods of time may affect device reliability. 2 Typical thermal impedance is JA = 45°C/W, JC = 41°C/W.
I. 100% Production Tested. II. 100% production tested at +25°C, and sample tested at specified temperatures. AC testing done on sample basis. III. Sample Tested Only. IV. Parameter is guaranteed by design and characterization testing. V. Parameter is a typical value only. VI. All devices are 100% production tested at +25°C, sample tested at temperature extremes.
+VS
50
50
ORDERING GUIDE
WRITE HOLD BIAS HOLD
Model
Temperature Range
Package Option R-28 R-28 (1000/reel)
SENSE IN
AD9660KR 0°C to +70°C AD9660KR-REEL 0°C to +70°C
PIN ASSIGNMENTS
WRITE CAL WRITE PULSE WRITE LEVEL VREF 1 2 3 4
T/H
1mA OFFSET SET
28 OFFSET PULSE 27 OFFSET SET 26 GROUND 25 +VS
+VS
VBANDGAP
WRITE HOLD 5 GROUND +VS SENSE IN GAIN 6 7 8 9
AD9660KR
24 OUTPUT
TOP VIEW 23 +VS (Not to Scale) 22 OUTPUT 21 +VS 20 OUTPUT 19 +VS 18 OUTPUT 17 GROUND 16 DISABLE 15 BIAS CAL
100 VREF 450 +VS
POWER MONITOR 10 +VS 11 GROUND 12 BIAS HOLD 13 BIAS LEVEL 14
1250
TTL INPUT +VS
OUTPUT
Equivalent Circuits
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD9660 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
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AD9660
PIN DESCRIPTIONS
Pin OUTPUT BIAS LEVEL
Function Analog laser diode current output. Connect to anode of laser diode, cathode connected to GROUND externally. Analog voltage input, VREF to VREF + 1.6 V. Bias current is set proportional to the BIAS LEVEL during calibration as follows: -V V
I MONITOR = 1. 85 × ( RGAIN + 50 )
BIAS LEVEL REF
BIAS CAL
TTL/CMOS compatible, Bias loop T/H control signal. Logic HIGH enables calibration mode, and the bias loop T/H immediately goes into track mode. Logic LOW disables the bias loop T/H and immediately places it in hold mode. WRITE PULSE should be held logic LOW while calibrating. Floats logic HIGH. External hold capacitor for the bias loop T/H. Approximate droop in the bias current while BIAS CAL is logic LOW is: ±I BIAS =
18 × 10
9
BIAS HOLD
t BIAS HOLD
CBIAS HOLD
. Bandwidth of the loop is: BW = 2 ( 550 ) C BIAS HOLD
1
WRITE PULSE WRITE CAL
TTL/CMOS compatible, current control signal. Logic HIGH supplies IMODULATION to the laser diode. Logic LOW turns IMODULATION off. Floats logic HIGH. TTL/CMOS compatible, write loop T/H control signal. Logic HIGH enables calibration mode; before enabling calibration the bias loop should be calibrated and OFFSET PULSE driven to an appropriate state. In calibration mode, 13 ns after the WRITE PULSE goes logic HIGH, the write loop T/H goes into track mode (there is no delay if WRITE PULSE is HIGH before WRITE CAL transitions to a HIGH level). The write loop T/H immediately goes into hold mode when the WRITE PULSE goes Logic LOW. WRITE CAL LOW disables the write loop T/H and places it in hold mode. Floats logic HIGH. Analog voltage input, VREF to VREF +1.6 V. Write current is set proportional to the input voltage during calibration as follows: I MONITOR =
VWRITE LEVEL - V REF 1. 85 × ( RGAIN + 50 )
WRITE LEVEL
WRITE HOLD
External hold capacitor for the write loop T/H. Approximate droop in IMODULATION current while WRITE CAL is logic LOW is: ±I MODULATED =
BW = 1 2 ( 550 ) CBIAS HOLD
18 × 10 tWRITE HOLD CWRITE HOLD
. Bandwidth of the loop is:
-9
SENSE IN
Analog current input, IMONITOR, from PIN photo detector diode. SENSE IN should be connected to the cathode of the PIN diode, with the PIN anode connected to GROUND or a negative voltage. Voltage at SENSE IN varies slightly with temperature and current, but is typically 4.0 V. External connection for the feedback network of the transimpedance amplifier. External feedback network, RGAIN and CGAIN, should be connected between GAIN and POWER MONITOR. See text for choosing values. Output voltage monitor of the internal feedback loop. Voltage is proportional to feedback current from photo diode.
GAIN POWER MONITOR
OFFSET Set resistor connection for the offset current source. Resistor between OFFSET CURRENT SET and +VS CURRENT SET determines offset current level. The input voltage at this node varies slightly with temperature and current, but is typically 1.4 V. See curves. Can also be driven with a current out DAC. OFFSET PULSE DISABLE TTL/CMOS compatible, OFFSET current control signal. Logic HIGH adds IOFFSET to IOUT. Logic LOW turns off IOFFSET. Floats logic HIGH. TTL/CMOS compatible, current output disable circuit. Logic LOW for normal operation; logic HIGH disables the current outputs to the laser diode, and drives the voltage on the hold capacitors close to VREF (minimizes the output current when the device is re-enabled). DISABLE floats logic HIGH. Analog Voltage Output, internal bandgap voltage reference, ~1.75 V, provided to user for power level offset. Positive Power Supply. Nominally +5 V, pin connections should be tied together externally. Ground Reference. All grounds should be tied together externally.
V REF + VS GROUND
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Typical Performance CharacteristicsAD9660
6.25mV
35 30 25 20
IOFFSET
193.8mV
20mV
2ns
15 10
ML64116R OUTPUT 50
TEK 11802 O'SCOPE
5
AD9660
120V ANTEL ARS1 PHOTO DETECTOR
0
50
0
5
10 15 ROFFSET k
20
25
Figure 2. IOFFSET vs. ROFFSET
Figure 1. Driving ML64116R Laser @ 30 mW
THEORY OF OPERATION
The AD9660 combines a very fast output current switch with onboard analog light power control loops to provide the user with a complete laser diode driver solution. The block diagram illustrates the key internal functions. The control loops of the AD9660, the bias loop and the write loop, adjust the output current level, IOUT, so that the photo diode feedback current, IMONITOR, out of SENSE IN is proportional to the analog input voltage at BIAS LEVEL or WRITE LEVEL. Since the monitor
WRITE HOLD
current is proportional to the laser diode light power, the loops effectively control laser power to a level proportional to the analog inputs. The control loops should be periodically calibrated independently (see Choosing CBIAS HOLD and CWRITE HOLD). The offset current generator produces an open loop output current, IOFFSET. Its level is controlled by an external set resistor or a current out DAC (see Figure 2). While IOFFSET is not calibrated as the currents from the bias and write loops are, it can be very versatile (see Offset Current below).
TTL DISABLE WRITE PULSE TTL
DISABLE CIRCUIT
AD9660
VOLT REF
VREFOUT
WRITE CAL
TTL
DELAY
*
WRITE LEVEL
ANALOG 5pF VREF V:1
WRITE LOOP
IMODULATION
1:10
IOUT
OUTPUT LASER DIODE
GAIN CGAIN RGAIN POWER MONITOR
50 2* IMONITOR ANALOG 1.85:1 TZA VREF 4.0V SENSE IN IMONITOR PHOTO DETECTOR
VREF BIAS LEVEL ANALOG 5pF TTL
IBIAS
V:1 1:10
BIAS LOOP
1:10
BIAS CAL BIAS HOLD OFFSET PULSE
IOFFSET
TTL 1.4V
OFFSET CURRENT SET +VS
* 10ns DELAY ON RISING
EDGE; 0ns ON FALLING
Figure 3. Functional Block Diagram
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