EL6206 ® Data Sheet June 10, 2004 Laser Driver Oscillator Features The EL6206 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. • Low power dissipation One external resistor sets the oscillator frequency. Another external resistor sets the oscillator amplitude. 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 bias 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. FN7340 • User-selectable frequency from 100MHz to 600MHz controlled with a single resistor • User-specified amplitude from 10mAPK-PK to 100mAPK controlled with a single resistor • Auto turn-off threshold • Soft edges for reduced EMI • Small 5-pin SOT23 package Applications • DVD players • DVD-ROM drives • CD-RW drives • MO drives • General purpose laser noise reduction This part is pin-compatible to the EL6201. It is superior to the EL6201 in several ways: It has up to 100mA output capability, it is faster (up to 600MHz), it is more powerefficient, it has less harmonic content, and it has an auto shut-off feature activated at 1.1V. Ordering Information EL6206CW-T7 5-Pin SOT23 7” (3K pcs) MDP0038 The part is available in the space-saving 5-pin SOT23 package. It is specified for operation from 0°C to +85°C. EL6206CW-T7A 5-Pin SOT23 7” (250 pcs) MDP0038 PART NUMBER PACKAGE TAPE & REEL PKG. DWG. # Pinout EL6206 (5-PIN SOT23) TOP VIEW 1 VDD 2 GND 3 IOUT 1 RFREQ 5 RAMP 4 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 © Intersil Americas Inc. 2004. All Rights Reserved. Elantec is a registered trademark of Elantec Semiconductor, Inc. All other trademarks mentioned are the property of their respective owners. EL6206 Absolute Maximum Ratings (TA = 25°C) 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 . . . . . . . . . . . 0°C to +85°C Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . +150°C Storage Temperature Range . . . . . . . . . . . . . . . . . .-65°C to +150°C Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100mAPK-PK Power Dissipation (max) . . . . . . . . . . . . . . . . . . . . . . . . See Curves CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. 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 & Reference Voltage Characteristics VDD = +5V, TA = 25°C, RL = 10Ω, RFREQ = 3.5kΩ (FOSC = 550MHz), RAMP = 2540Ω (IOUT = 50mAP-P measured at 100MHz), VOUT = 2.2V PARAMETER DESCRIPTION CONDITIONS MIN TYP UNIT 5.5 V PSOR Power Supply Operating Range ISO Supply Current Disabled VOUT < VCUTOFF 550 750 µA ISTYP Supply Current Typical Conditions RFREQ = 3.5kΩ, RAMP = 2.54kΩ 22 TBD mA ISLO Supply Current Low Conditions RFREQ = 18.2kΩ, RAMP = 12.7kΩ 6 mA VFREQ Voltage at RFREQ Pin 1.27 V VRAMP Voltage on RAMP Pin 1.27 V VCUTOFF Monitoring Voltage of IOUT Pin Oscillator Characteristics 4.5 MAX 1.1 1.4 V VDD = +5V, TA = 25°C, RL = 10Ω, RFREQ = 3.5kΩ (FOSC = 550MHz), RAMP = 2540Ω (IOUT = 50mAP-P measured at 100MHz), VOUT = 2.2V PARAMETER DESCRIPTION CONDITIONS MIN TYP MAX UNIT TBD 550 TBD MHz FOSC Frequency Tolerance Unit-unit frequency variation FLOW Frequency Range Low RFREQ = 18.2kΩ 100 MHz TCOSC Frequency Temperature Sensitivity -40°C to +85°C ambient 50 ppm/°C PSRROSC Frequency Change ∆F/F VDD from 4.5V to 5.5V 1 % Driver Characteristics VDD = +5V, TA = 25°C, RL = 10Ω, RFREQ = 18.2kΩ (FOSC = 100MHz), RAMP = 2540Ω (IOUT = 50mAP-P measured at 100MHz), VOUT = 2.2V PARAMETER DESCRIPTION CONDITIONS MIN TYP MAX UNIT AMPHIGH Amplitude Range High RAMP = 1.27kΩ 100 mAP-P AMPLOW Amplitude Range Low RAMP = 12.7kΩ 10 mAP-P IOSNOM Offset Current @ 2.2V RFREQ = 3.5kΩ, VOUT = 2.2V TBD mA IOSHIGH Offset Current @ 2.8V RFREQ = 3.5kΩ, VOUT = 2.8V TBD mA IOSLOW Offset Current @ 1.8V RFREQ = 3.5kΩ, VOUT = 1.8V TBD mA IOUTP-P Output Current Tolerance Defined as one standard deviation 2 % Duty Cycle Output Push Time/Cycle Time RFREQ = 3.5kΩ 43 % PSRRAMP Amplitude Change of Output ∆I/I VDD from 4.5V to 5.5V -54 dB TON Auto Turn-on Time Output voltage step from 0V to 2.2V 15 µs TOFF Auto Turn-off Time Output voltage step from 2.2V to 0V 0.5 µs IOUTN Output Current Noise Density RFREQ = 5210Ω, measured @ 10MHz 2.5 nA/√Hz 2 EL6206 Pin Descriptions PIN NAME PIN TYPE PIN DESCRIPTION 1 VDD Positive power for laser driver (4.5V - 5.5V) 2 GND Chip ground pin (0V) 3 IOUT Current output to laser diode 4 RAMP Set pin for output current amplitude 5 RFREQ Set pin for oscillator frequency Recommended Operating Conditions VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V ±10% VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2V - 3V RFREQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3kΩ (min) RAMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25kΩ (min) FOSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100-600MHz IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-100mAPK-PK IOUT Control VOUT IOUT Less than VCUTOFF OFF More than VCUTOFF Normal Operation Typical Performance Curves VDD = 5V, TA = 25°C, RL = 10Ω, RFREQ = 3.5kΩ, RAMP = 2.54kΩ, VOUT = 2.2V unless otherwise specified. FREQUENCY vs RFREQ FREQUENCY vs 1 / RFREQ 700 700 Frequency=1824 * 1kΩ / RFREQ (MHz) 600 600 500 500 FREQUENCY (MHz) FREQUENCY (MHz) Frequency=1824 * 1kΩ / RFREQ (MHz) 400 300 200 100 400 300 200 100 0 0 0 5 10 15 20 25 30 35 0 0.05 RFREQ (kΩ) 0.1 0.15 0.2 1kΩ / RFREQ Block Diagram VDD 1 GND 2 IOUT 3 3 DRIVER OSCILLATOR 5 RFREQ AUTO SHUT-OFF REFERENCE AND BIAS 4 RAMP 0.25 0.3 0.35 EL6206 Typical Application Circuit TYPICAL ROM LASER DRIVER EMI REDUCTION SUPPLY FILTER GAIN SETTING RESISTOR +5V BEAD 4.7µF 0.1µF PNP IAPC VDD1 2 GND 3 IOUT RFREQ 5 RFREQ BEAD CONTROLLER GND 0.1µF EMI REDUCTION FILTER MAIN BOARD 1 FLEX RAMP 4 RAMP Laser Diode PHOTO DIODE AMPLITUDE SETTING RESISTOR ON PICKUP ~10mW LASER OUTPUT POWER LASER OUTPUT POWER THRESHOLD CURRENT IAPC 0mW 0mA ~60mA LASER CURRENT OSCILLATOR CURRENT 4 FREQUENCY SETTING RESISTOR EL6206 Applications Information Product Description The EL6206 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 EL6206 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 EL6206 has the operating frequency from 100MHz to 600MHz and the output current from 10mAP-P to 100mAP-P. The supply current is only 22mA for the output current of 50mAP-P at the operating frequency of 550MHz. 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 Value Setting The laser should always have a forward current during operation. This will prevent the laser voltage from collapsing, 5 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). 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 EL6206'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 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 EL6206's local environment from propagating to the modulation source, and it will keep parasitic capacitance at the pin minimized. EL6206 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: 70Ω reactance at 300MHz EL6206 0.1µF Chip T JMAX – T AMAX P DMAX = -------------------------------------------Θ JA where PDMAX = Maximum Power Dissipation in the Package TJMAX = Maximum Junction Temperature +5V VS The maximum power dissipation allowed in a package is determined according to: TAMAX = Maximum Ambient Temperature 0.1µF Chip θJA = Thermal Resistance of the Package GND The supply current of the EL6206 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: FIGURE 2. RECOMMENDED SUPPLY BYPASSING Also important is circuit-board layout. At the EL6206'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. × 1kΩ- + --------------------------------30mA × 1kΩ- + 0.6mA -----------------------------------------I SUP = 31.25mA R AMP R FREQ The power dissipation can be calculated from the following equation: P D = V SUP × I SUP RFREQ SUPPLY BYPASS RAMP SOURCING CURRENT LOOP SINKING CURRENT LOOP GND LASER DIODE FIGURE 3. OUTPUT CURRENT LOOPS 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 θJA, and lower power dissipation would then be required. For the pushing current loop, the current flows through the bypass capacitor, into the EL6206 supply pin, out the IOUT pin to the laser, and from the laser back to the decoupling capacitor. This loop should be small. JEDEC JESD51-3 LOW EFFECTIVE THERMAL CONDUCTIVITY TEST BOARD 0.6 Power Dissipation With the high output drive capability, the EL6206 is possible to exceed the 125°C “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. 6 POWER DISSIPATION (W) 0.5 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. 488mW 0.4 θ 5Pi n JA = 25 0.3 SO T2 3 6° C/ W 0.2 0.1 0 0 25 50 75 85 100 125 150 AMBIENT TEMPERATURE (°C) FIGURE 4. PACKAGE POWER DISSIPATION VS AMBIENT TEMPERATURE EL6206 JEDEC JESD51-7 HIGH EFFECTIVE THERMAL CONDUCTIVITY TEST BOARD 0.6 POWER DISSIPATION (W) 0.5 543mW θ 5Pi n SO T2 23 3 0° C/ W JA = 0.4 0.3 0.2 0.1 0 0 25 50 75 85 100 125 150 AMBIENT TEMPERATURE (°C) FIGURE 5. PACKAGE POWER DISSIPATION VS AMBIENT TEMPERATURE All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality 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. 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