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EL6204
Data Sheet July 11, 2007 FN7219.2
Laser Driver Oscillator
The EL6204 is a push-pull oscillator used to reduce laser noise. It uses the standard interface to existing ROM controllers. The frequency and amplitude are each set with a separate resistor connected to ground. The tiny package and harmonic reduction allow the part to be placed close to a laser with low RF emissions. An auto turn-off feature allows it to easily be used on combo CD-RW plus DVD-ROM pickups. If the APC current is reduced such that the average laser voltage drops to less than 1.1V, the output and oscillator are disabled, reducing power consumption to a minimum. The current drawn by the oscillator consists of a small utility current, plus the peak output amplitude in the positive cycle. In the negative cycle the oscillator subtracts peak output amplitude from the laser APC current. The EL6204 part is available in the space-saving 6 Ld SOT23 package and is specified for operation from 0C to +70C.
Features
* Low power dissipation * User-selectable frequency from 60MHz to 600MHz controlled with a single resistor * User-specified amplitude from 10mAPK-PK to 100mAPK-PK controlled with a single resistor * Auto turn-off threshold * Soft edges for reduced EMI * Small 6 Ld SOT-23 package
Applications
* DVD players * DVD-ROM drives * CD-RW drives * MO drives * General purpose laser noise reduction * Local oscillators
Pinout
EL6204 (6-PIN SOT-23) TOP VIEW
1 2 3 IOUT VDD GND1 RFREQ GND2 RAMP 6 5 4
Ordering Information
PART NUMBER EL6204CW-T7* EL6204CW-T7A* EL6204CWZ-T7* (Note) PART MARKING T T BNAA PACKAGE PKG. DWG. #
6 Ld SOT-23 MDP0038 6 Ld SOT-23 MDP0038 6 Ld SOT-23 MDP0038 (Pb-free) 6 Ld SOT-23 MDP0038 (Pb-free)
EL6204CWZ-T7A* (Note) BNAA
*Please refer to TB347 for details on reel specifications. NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright (c) Intersil Americas Inc. 2004-2007. All Rights Reserved. Elantec is a registered trademark of Elantec Semiconductor, Inc. All other trademarks mentioned are the property of their respective owners.
EL6204
Absolute Maximum Ratings (TA = +25C)
Voltages Applied to: VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to +6.0V IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to +6.0V RFREQ, RAMP . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to +6.0V Operating Ambient Temperature Range . . . . . . . . . . . 0C to +70C Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . +150C Storage Temperature Range . . . . . . . . . . . . . . . . . .-65C to +150C Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100mAPK-PK Power Dissipation (max) . . . . . . . . . . . . . . . . . . . . . . . . See Curves Pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . .see link below http://www.intersil.com/pbfree/Pb-FreeReflow.asp
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and result in failures not covered by warranty. IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
Supply and Reference Voltage CharacteristicsVDD = +5V, TA = +25C, RL = 10, RFREQ = 5210 (FOSC = 350MHz), RAMP =
2540 (IOUT = 50mAP-P measured at 60MHz), VOUT = 2.2V PARAMETER PSOR ISO ISTYP ISLO ISHI VFREQ VRAMP VCUTOFF DESCRIPTION Power Supply Operating Range Supply Current Disabled Supply Current Typical Conditions Supply Current Low Conditions Supply Current High Conditions Voltage at RFREQ Pin Voltage on RAMP Pin Monitoring Voltage of IOUT Pin 1.1 VOUT < VCUTOFF RFREQ = 5.21k, RAMP = 2.54k RFREQ = 30.5k, RAMP = 12.7k RFREQ = 3.05k, RAMP = 1.27k CONDITIONS MIN 4.5 550 18.5 4.75 32 1.27 1.27 1.4 TYP MAX 5.5 750 22 UNIT V A mA mA mA V V V
Oscillator Characteristics
PARAMETER FOSC FHIGH FLOW TCOSC PSRROSC
VDD = +5V, TA = 25C, RL = 10, RFREQ = 5210 (FOSC = 350MHz), RAMP = 2540 (IOUT = 50mAP-P measured at 60MHz), VOUT = 2.2V CONDITIONS Unit-unit frequency variation RFREQ = 3.05k RFREQ = 30.5k 0C to +70C ambient VDD from 4.5V to 5.5V MIN 300 TYP 350 600 60 50 1 MAX 400 UNIT MHz MHz MHz ppm/C %
DESCRIPTION Frequency Tolerance Frequency Range High Frequency Range Low Frequency Temperature Sensitivity Frequency Change F/F
Driver Characteristics
PARAMETER AMPHIGH AMPLOW IOSNOM IOSHIGH IOSLOW IOUTP-P Duty Cycle PSRRAMP TON TOFF IOUTN
VDD = +5V, TA = +25C, RL = 10, RFREQ = 30.5k (FOSC = 60MHz), RAMP = 2540 (IOUT = 50mAP-P measured at 60MHz), VOUT = 2.2V CONDITIONS RAMP = 1.27k RAMP = 12.7k RFREQ = 5210, VOUT = 2.2V RFREQ = 5210, VOUT = 2.8V RFREQ = 5210, VOUT = 1.8V Defined as one standard deviation RFREQ = 5210 VDD from 4.5V to 5.5V Output voltage step from 0V to 2.2V Output voltage step from 2.2V to 0V RFREQ = 5210, measured @ 10MHz MIN TYP 100 10 -4 -4.8 -3.5 2 43 -54 15 0.5 2.5 MAX UNIT mAP-P mAP-P mA mA mA % % dB s s nA/Hz
DESCRIPTION Amplitude Range High Amplitude Range Low Offset Current @ 2.2V Offset Current @ 2.8V Offset Current @ 1.8V Output Current Tolerance Output Push Time/Cycle Time Amplitude Change of Output I/I Auto Turn-on Time Auto Turn-off Time Output Current Noise Density
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EL6204 Pin Descriptions
PIN NAME 1 2 3 4 5 6 PIN TYPE IOUT VDD GND1 RAMP GND2 RFREQ Current output to laser diode Positive power for laser driver (4.5V - 5.5V) Chip ground pin (0V for output) Set pin for output current amplitude Chip ground pin (0V for RFREQ, RAMP) Set pin for oscillator frequency PIN DESCRIPTION
Recommended Operating Conditions
VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V 10% VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2V to 3V RFREQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3k (min) RAMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25k (min) FOSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60 to 600MHz IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 to 100mAPK-PK
IOUT Control
VOUT Less than VCUTOFF More than VCUTOFF IOUT OFF Normal Operation
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EL6204 Typical Performance Curves
VDD = 5V, TA = 25C, RL = 10, RFREQ = 5.21k, RAMP = 2.54k, VOUT = 2.2V unless otherwise specified.
Frequency Distribution 500 Typical Production Distortion 8 7 6 Number of Parts 5 4 3 2 1 0 310 318 326 334 342 350 358 366 374 382 390 0 6 18 30 42 54 66 78 90 0.35 0.8 0.9 Measured from -40C to +85C Frequency Drift with Temperature
400 Number of Parts
300
200
100
Frequency (MHz) Frequency vs RFREQ 700 Frequency=1824 * 1k / RFREQ (MHz) 600 500 Frequency (MHz) 400 300 200 100 0 0 5 10 15 20 25 30 35 RFREQ (k) Frequency (MHz) 600 500 400 300 200 100 0 0 0.05 700
Frequency TC (ppm/C) Frequency vs 1 / RFREQ
Frequency=1824 * 1k / RFREQ (MHz)
0.1
0.15
0.2
0.25
0.3
1k / RFREQ
Output Current vs RAMP 180 160 140 Output Current (mA) 120 100 80 60 40 20 0 0 2 4 6 8 10 12 14 RAMP (k) Amplitude PK-PK=127 * 1k / RAMP (mA) measured @60MHz (over-shoot not included) IOUT PK-PK measured @60/350/600MHz (over-shoot included) Output Current (mA) 180 160 140 120 100 80 60 40 20 0
Output Current vs 1 / RAMP
IOUT PK-PK measured @60/350/600MHz (over-shoot included)
Amplitude PK-PK= 127 * 1k / RAMP (mA) measured @60MHz (over-shoot not included) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
1k / RAMP
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EL6204 Typical Performance Curves
Supply Current vs RFREQ 25 35 30 Supply Current (mA) 20 Supply Current (mA) 25 20 15 10 0 0 5 10 15 20 25 30 35 RFREQ (k) 0 0 5 10 15 20 25 30 35 RAMP (k)
(Continued)
Supply Current vs RAMP
15
Frequency vs Supply Voltage 360 100
Peak-to-Peak Output Current vs Supply Voltage
355 Frequency (MHz) IOUT PK-PK (mA) 4.6 4.8 5 5.2 5.4 5.6
95
350
90
345
85
340 4.4
80 4.4
4.6
4.8
5
5.2
5.4
5.6
Supply Voltage (V)
Supply Voltage (V)
Supply Current vs Supply Voltage 21 400
Frequency vs Temperature
20 Supply Current (mA) Frequency (MHz) 4.6 4.8 5 5.2 5.4 5.6
380
360
19
340
18
320
17 4.4
300 -50
0
50 Ambient Temperature (C)
100
150
Supply Voltage (V)
5
EL6204 Typical Performance Curves
(Continued)
Peak-to-Peak Output Current vs Temperature 95 90 Supply Current (mA) 85 IOUT PK-PK (mA) 80 75 70 65 60 -50 25 30
Supply Current vs Temperature
20
15
0
50 Ambient Temperature (C)
100
150
10 -50
0
50 Ambient Temperature (C)
100
150
Output Current @ 60MHz
Output Current @ 350MHz
40mA
4.0ns
40mA
1.0ns
RFREQ=30.3k RAMP=2.54k
RFREQ=2.51k RAMP=2.54k
Output Current @ 600MHz 10 40mA 0.4ns -10 Relative Amplitude (dB)
Output Spectrum-Wideband
-30
-50
-70 RFREQ=3.03k RAMP=2.54k -90 340 344 348 352 356 360
Frequency (MHz)
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EL6204 Block Diagram
IOUT
1
DRIVER
OSCILLATOR
6
RFREQ
VDD
2
5
GND2
GND1
3
AUTO SHUT-OFF
REFERENCE AND BIAS
4
RAMP
Typical Application Circuit
Typical ROM Laser Driver Gain Setting Resistor EMI Reduction Filters
IAPC PNP
BEAD
Frequency Setting Resistor RFREQ
0.1F BEAD +5V Controller 4.7F GND 0.1F 0.1F Laser Diode
1 2 3
IOUT VDD GND1
RFREQ GND2 RAMP
6 5 RAMP 4
RF Blocking Resistor
Photo Diode
Amplitude Setting Resistor
Main Board
Flex
On Pickup
~10mW
Laser Output Power
Laser Output Power
Threshold Current
IAPC 0mW 0mA ~60mA Laser Current
Oscillator Current
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EL6204 Applications Information
Product Description
The EL6204 is a solid state, low-power, high-speed laser modulation oscillator with external resistor-adjustable operating frequency and output amplitude. It is designed to interface easily to laser diodes to break up optical feedback resonant modes and thereby reduce laser noise. The output of the EL6204 is composed of a push-pull current source, switched alternately at the oscillator frequency. The output and oscillator are automatically disabled for power saving when the average laser voltage drops to less than 1.1V. The EL6204 has the operating frequency from 60MHz to 600MHz and the output current from 10mAP-P to 100mAP-P. The supply current is only 18.5mA for the output current of 50mAP-P at the operating frequency of 350MHz. and ensure that the high frequency components reach the junction without having to charge the junction capacitance. Generally it is desirable to make the oscillator currents as large as possible to obtain the greatest reduction in laser noise. But it is not a trivial matter to determine this critical value. The amplitude depends on the wave shape of the oscillator current reaching the laser junction. If the output current is sinusoidal, and the components in the output circuit are fixed and linear, then the shape of the current will be sinusoidal. But the amount of current reaching the laser junction is a function of the circuit parasitics. These parasitics can result in a resonant increase in output depending on the frequency due to the junction capacitance and layout. Also, the amount of junction current causing laser emission is variable with frequency due to the junction capacitance. In conclusion, the sizes of the RAMP and RFREQ resistors must be determined experimentally. A good starting point is to take a value of RAMP for a peak-to-peak current amplitude less than the minimum laser threshold current and a value of RFREQ for an output current close to a sinusoidal wave form (refer to the proceeding performance curves).
Theory of Operation
A typical semiconductor laser will emit a small amount of incoherent light at low values of forward laser current. But after the threshold current is reached, the laser will emit coherent light. Further increases in the forward current will cause rapid increases in laser output power. A typical threshold current is 35mA and a typical slope efficiency is 0.7mW/mA. When the laser is lasing, it will often change its mode of operation slightly, due to changes in current, temperature, or optical feedback into the laser. In a DVD-ROM, the optical feedback from the moving disk forms a significant noise factor due to feedback-induced mode hopping. In addition to the mode hopping noise, a diode laser will roughly have a constant noise level regardless of the power level when a threshold current is exceeded. The oscillator is designed to produce a low noise oscillating current that is added to the external DC current. The effective AC current is to cause the laser power to change at the oscillator frequency. This change causes the laser to go through rapid mode hopping. The low frequency component of laser power noise due to mode hopping is translated up to sidebands around the oscillator frequency by this action. Since the oscillator frequency can be filtered out of the low frequency read and serve channels, the net result is that the laser noise seems to be reduced. The second source of laser noise reduction is caused by the increase in the laser power above the average laser power during the pushingcurrent time. The signal-to-noise ratio (SNR) of the output power is better at higher laser powers because of the almost constant noise power when a threshold current is exceeded. In addition, when the laser is off during the pulling-current time, the noise is also very low.
RAMP and RFREQ Pin Interfacing
Figure 1 shows an equivalent circuit of pins associated with the RAMP and RFREQ resistors. VREF is roughly 1.27V for both RAMP and RFREQ. The RAMP and RFREQ resistors should be connected to the non-load side of the power ground to avoid noise pick-up. These resistors should also return to the EL6204's ground very directly to prevent noise pickup. They also should have minimal capacitance to ground. Trimmer resistors can be used to adjust initial operating points.
+ VREF -
PIN
FIGURE 1. RAMP AND RFREQ PIN INTERFACE
RAMP and RFREQ Value Setting
The laser should always have a forward current during operation. This will prevent the laser voltage from collapsing,
External voltage sources can be coupled to the RAMP and RFREQ pins to effect frequency or amplitude modulation or adjustment. It is recommended that a coupling resistor of 1k be installed in series with the control voltage and mounted directly next to the pin. This will keep the inevitable highfrequency noise of the EL6204's local environment from propagating to the modulation source, and it will keep parasitic capacitance at the pin minimized.
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EL6204
Supply Bypassing and Grounding
The resistance of bypass-capacitors and the inductance of bonding wires prevent perfect bypass action, and 150mVP-P noise on the power lines is common. There needs to be a lossy bead inductance and secondary bypass on the supply side to control signals from propagating down the wires. Figure 2 shows the typical connection.
L Series: 70 reactance at 300MHz VS EL6204 GND 0.1F Chip +5V 0.1F Chip
The maximum power dissipation allowed in a package is determined according to:
T JMAX - T AMAX P DMAX = ------------------------------------------- JA
where PDMAX = Maximum power dissipation in the package TJMAX = Maximum junction temperature TAMAX = Maximum ambient temperature JA = Thermal resistance of the package The supply current of the EL6204 depends on the peak-topeak output current and the operating frequency which are determined by resistors RAMP and RFREQ. The supply current can be predicted approximately by the following equation:
31.25mA x 1k 30mA x 1k I SUP = ------------------------------------------ + ---------------------------------- + 0.6mA R FREQ R AMP
FIGURE 2. RECOMMENDED SUPPLY BYPASSING
Also important is circuit-board layout. At the EL6204's operating frequencies, even the ground plane is not lowimpedance. High frequency current will create voltage drops in the ground plane. Figure 3 shows the output current loops.
RFREQ RAMP
The power dissipation can be calculated from the following equation:
P D = V SUP x I SUP
Supply Bypass
Sourcing Current Loop
GND
Sinking Current Loop
Laser Diode
FIGURE 3. OUTPUT CURRENT LOOPS
For the pushing current loop, the current flows through the bypass capacitor, into the EL6204 supply pin, out the IOUT pin to the laser, and from the laser back to the decoupling capacitor. This loop should be small. For the pulling current loop, the current flows into the IOUT pin, out of the ground pin, to the laser cathode, and from the laser diode back to the IOUT pin. This loop should also be small.
Here, VSUP is the supply voltage. Figures 4 and 5 provide a convenient way to see if the device will overheat. The maximum safe power dissipation can be found graphically, based on the package type and the ambient temperature. By using the previous equation, it is a simple matter to see if PD exceeds the device's power derating curve. To ensure proper operation, it is important to observe the recommended derating curve shown in Figures 4 and 5. A flex circuit may have a higher JA, and lower power dissipation would then be required.
Package Power Dissipation vs Ambient Temperature JEDEC JESD51-3 Low Effective Thermal Conductivity Test Board 0.6 0.5 Power Dissipation (W) 488mW 0.4 0.3 0.2 0.1 0 0 25 50 75 85 100 125 150 Ambient Temperature (C)
6JA =
Pi n
25 6
Power Dissipation
With the high output drive capability, the EL6204 is possible to exceed the 125C "absolute-maximum junction temperature" under certain conditions. Therefore, it is important to calculate the maximum junction temperature for the application to determine if the conditions need to be modified for the oscillator to remain in the safe operating area.
C /W
SO T2
3
FIGURE 4. PACKAGE POWER DISSIPATION vs AMBIENT TEMPERATURE
9
EL6204
Package Power Dissipation vs Ambient Temperature JEDEC JESD51-7 High Effective Thermal Conductivity Test Board 0.6 0.5 Power Dissipation (W) 0.4 0.3 0.2 0.1 0 0 25 50 75 85 100 125 150 Ambient Temperature (C) 543mW
JA
SO T=2 23 30 C /W
6Pi n
FIGURE 5. PACKAGE POWER DISSIPATION vs AMBIENT TEMPERATURE
10
EL6204 SOT-23 Package Family
e1 A N 6 4
MDP0038
D
SOT-23 PACKAGE FAMILY MILLIMETERS SYMBOL A A1 SOT23-5 1.45 0.10 1.14 0.40 0.14 2.90 2.80 1.60 0.95 1.90 0.45 0.60 5 SOT23-6 1.45 0.10 1.14 0.40 0.14 2.90 2.80 1.60 0.95 1.90 0.45 0.60 6 TOLERANCE MAX 0.05 0.15 0.05 0.06 Basic Basic Basic Basic Basic 0.10 Reference Reference Rev. F 2/07 NOTES:
E1 2 3
E
A2 b c
0.20 C
0.15 C D 2X 5 e B b NX 1 2 3 2X 0.20 M C A-B D
D E E1 e e1 L L1 N
0.15 C A-B 2X C D
1
3
A2 SEATING PLANE 0.10 C NX A1
1. Plastic or metal protrusions of 0.25mm maximum per side are not included. 2. Plastic interlead protrusions of 0.25mm maximum per side are not included. 3. This dimension is measured at Datum Plane "H". 4. Dimensioning and tolerancing per ASME Y14.5M-1994. 5. Index area - Pin #1 I.D. will be located within the indicated zone (SOT23-6 only).
(L1)
H
6. SOT23-5 version has no center lead (shown as a dashed line).
A
GAUGE PLANE c L 0 +3 -0
0.25
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Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries 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 Intersil or its subsidiaries.
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