1
®
FN7218
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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EL6203
Laser Driver Oscillator
The EL6203 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
har monic 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 pick-
ups.
One external resistor sets the oscillator frequency. Another
e xternal resistor sets the oscillator amplitude. If the APC
current is reduced such that the aver age 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.
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 more power-efficient, it has less harmonic
content, and it has an auto shut-off feature activated at 1.1V.
The part is available in the space-saving 5-pin SOT-23
package. It is specified for operation from 0°C to +70°C.
Pinout EL6203
(5-PIN SOT-23)
TOP VIEW
Features
• Low power dissipation
• User-selectable frequency from 60MHz 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 SOT-23 package
Applications
•DVD players
• DVD-ROM drives
• CD-RW drives
• MO drives
• General purpose laser noise reduction
*EL6203CW symbol is .Zxxx where xxx represents date code
1
2
3
5
4
VDD RFREQ
GND
IOUT RAMP
Ordering Information
PART NUMBER PACKAGE TAPE & REEL PKG. NO.
EL6203CW 5-Pin SOT-23* - MDP0038
EL6203CW-T7 5-Pin SOT-23* 7” MDP0038
EL6203CW-T13 5-Pin SOT-23* 13” MDP0038
Data Sheet November 15, 2002
2
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 +70°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 per manent damage to the device. This is a stress only rating and operation of the
device at these or any other conditi ons above those indicated in t he operational sections of this specification is not implied.
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for infor mation purposes only. Unless otherwise noted, all tests
are at the specified temperature and are pulsed tests, the refore: TJ = TC = TA
Supply & Reference Voltage Characteristics VDD = +5V, TA = 25°C, RL = 10Ω, RFREQ = 5210Ω (FOSC = 350MHz), RAMP =
2540Ω (IOUT = 50mAP-P measured at 60MHz), VOUT = 2.2V
PARAMETER DESCRIPTION CONDITIONS MIN TYP MAX UNIT
PSOR Power Supply Operating Range 4.5 5.5 V
ISO Supply Current Disabled VOUT < VCUTOFF 550 750 µA
ISTYP Supply Current Typical Conditions RFREQ = 5.21kΩ, RAMP = 2.54kΩ18.5 22 mA
ISLO Supply Current Low Conditions RFREQ = 30.5kΩ, RAMP = 12.7kΩ4.75 mA
ISHI Supply Current High Conditions RFREQ = 3.05kΩ, RAMP = 1.27kΩ32 mA
VFREQ Voltage at RFREQ Pin 1.27 V
VRAMP Voltage on RAMP Pin 1.27 V
VCUTOFF Monitoring Voltage of IOUT Pin 1.1 1.4 V
Oscillator Characteristics VDD = +5V, TA = 25°C, RL = 10Ω, RFREQ = 5210Ω (FOSC = 350MHz), RAMP = 2540Ω (IOUT = 50mAP-P
measured at 60MHz), VOUT = 2.2V
PARAMETER DESCRIPTION CONDITIONS MIN TYP MAX UNIT
FOSC Frequency Tolerance Unit-unit frequency variation 300 350 400 MHz
FHIGH Frequency Range High RFREQ = 3.05kΩ600 MHz
FLOW Frequency Range Low RFREQ = 30.5kΩ60 MHz
TCOSC Frequency Temperature Sensitivity 0°C to +70°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 = 30.5kΩ (FOSC = 60MHz), RAMP = 2540Ω (IOUT = 50mAP-P
measured at 60MHz), VOUT = 2.2V
PARAMETER DESCRIPTION CONDITIONS MIN TYP MAX UNIT
AMPHIGH Amplitude Range High RAMP = 1.27kΩ100 mAP-P
AMPLOW Amplitude Range Low RAMP = 12.7kΩ 10 mAP-P
IOSNOM Offset Current @ 2.2V RFREQ = 5210Ω, VOUT = 2.2V -4 mA
IOSHIGH Offset Current @ 2.8V RFREQ = 5210Ω, VOUT = 2.8V -4.8 mA
IOSLOW Offset Current @ 1.8V RFREQ = 5210Ω, VOUT = 1.8V -3.5 mA
IOUTP-P Output Current Tolerance Defined as one standard deviation 2 %
Duty Cycle Output Push Time/Cycle Time RFREQ = 5210Ω43 %
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
IOUTNOutput Current Noise Density RFREQ = 5210Ω, measured @ 10MHz 2.5 nA/√Hz
EL6203
3
Recommended Operating Conditions
VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V ±10%
VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2V - 3V
RFREQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3kΩ (min)
RAMP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25kΩ (min)
FOSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60-600MHz
IOUT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-100mAPK-PK
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
IOUT Control
VOUT IOUT
Less than VCUTOFF OFF
More than VCUTOFF Normal Operation
EL6203
4
Typical Performance Curves
VDD = 5V, TA = 25°C, RL = 10Ω, RFREQ = 5.21kΩ, RAMP = 2.54kΩ, VOUT = 2.2V unless otherwise specified.
Frequency (MHz)
0
200
400
500
600
700
RFREQ (kΩ)
0
Frequency vs RFREQ
5 15253510 20 30
100
300
Frequency=1824 * 1kΩ / RFREQ (MHz)
Frequency (MHz)
0
200
400
500
600
700
1kΩ / RFREQ
0
Frequency vs 1 / RFREQ
0.05 0.15 0.25 0.350.1 0.2 0.3
100
300
Frequency=1824 * 1kΩ / RFREQ (MHz)
Output Current (mA)
0
40
80
120
160
180
RAMP (kΩ)
0
Output Current vs RAMP
2 6 10 144812
20
60
Output Current (mA)
0
40
80
120
160
180
1kΩ / RAMP
0
Output Current vs 1 / RAMP
0.1 0.5 0.7 0.90.3 0.6 0.8
20
60
100
140
100
140
0.2 0.4
Number of Parts
0
100
500
Frequency (MHz)
310
Frequency Distribution
318
334
350
366
326
342
358
200
300
400
374
382
390
Typical
Production
Distortion
Number of Parts
0
1
8
Frequency TC (ppm/°C)
6
Frequency Drift with T emperature
30
54
18
42
3
5
7
66
78
90
Measured from
-40°C to +85°C
2
4
6
(over-shoot included)
Amplitude PK-PK=127 * 1kΩ / RAMP (mA)
measured @60MHz
(over-shoot not included)
IOUT PK-PK measured @60/350/600MHz
(over-shoot included)
(over-shoot not included)
IOUT PK-PK measured @60/350 /60 0M Hz
Amplitude PK-PK=
127 * 1kΩ / RAMP (mA)
measured @60MHz
EL6203
5
Typical Performance Curves (Continued)
Frequency (MHz)
340
345
355
360
Supply Voltage (V)
4.4
Frequency vs Supply Voltage
4.6 4.8 5.2 5.655.4
350
IOUT PK-PK (mA)
80
85
95
100
Supply Voltage (V)
4.4
Peak-to-Peak Output Current vs Supply Voltage
4.6 4.8 5.2 5.655.4
90
Supply Current (mA)
0
20
25
RFREQ (kΩ)
0
Supply Current vs RFREQ
515253510 20 30
15
Supply Current (mA)
0
25
35
RAMP (kΩ)
0
Supply Current vs RAMP
515253510 20 30
15
20
30
10
Supply Current (mA)
17
18
20
21
Supply Voltage (V)
4.4
Supply Current vs Supply Voltage
4.6 4.8 5.2 5.655.4
19
Frequency (MHz)
300
320
380
400
Ambient Temperature (°C)
-50
Frequency vs Temperature
015050 100
340
360
EL6203
6
Typical Performance Curves (Continued)
Supply Current (mA)
10
15
30
Ambient Temperature (°C)
-50
Supply Current vs Temperature
015050 100
20
25
Peak-to-Peak Output Current vs Temperature
Output Current @ 60MHz Output Current @ 350MHz
Output Current @ 600MHz
RFREQ=30.3kΩ
RAMP=2.54kΩ
40mA 4.0ns
RFREQ=2.51kΩ
RAMP=2.54kΩ
40mA 1.0ns
RFREQ=3.03kΩ
RAMP=2.54kΩ
40mA 0.4ns
IOUT PK-PK (mA)
60
70
95
Ambient Temperature (°C)
-50 0 15050 100
80
90
65
75
85
Relative Amplitude (dB)
-90
10
Frequency (MHz)
340
Output Spectrum-Wideband
360
-30
-70
-10
-50
348 352 356344
EL6203
7
Block Diagram
Typical Application Circuit
1
2
3
5
4
AUTO SHUT-OFF
DRIVER
REFERENCE
AND BIAS
OSCILLATORVDD
GND
IOUT
RFREQ
RAMP
1
2
3
5
4
VDD1 RFREQ
GND
IOUT RAMP
Controller
Frequency
Setting
Resistor
EMI
Reduction
Supply Filter
Gain
Setting
Resistor
Typical
ROM Laser
Driver
Laser Diode
Photo Diode
BEAD+5V
GND
4.7µF
Amplitude
Setting
Resistor
0.1uF
PNP
BEAD
0.1uF
EMI
Reduction
Filter
Main Board On PickupFlex
Laser Output
Power
Laser Current
0mW
~10mW
0mA ~60mA
Oscillator Current
Laser Output Power
Threshold Current
IAPC
RFREQ
RAMP
IAPC
EL6203
8
Applications Information
Product Description
The EL6203 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 EL6203 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 av er age laser v oltage drops to less than 1.1V. The
EL6203 has the operating frequency from 60MHz to
600MHz and the output current from 10mAP-P to 100mAP-P.
The supply curren t is only 18.5mA for the output current of
50mAP-P at the operating frequency of 350MHz.
Theory of Operation
A typical semiconductor laser will emit a small amoun t 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 feedbac k into the laser. In a DVD-ROM, the optical
feedback from the moving disk forms a significant noise
f actor due to feedback-induced mode hopping. In addition to
the mode hopping noise, a diode laser will roughl y 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
eff ectiv e 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 sou rce of
laser noise reduction is caused by the increase in the laser
power above the average laser power during the pushing-
current 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 dur ing the pulling-current
time, the noise is al so very low.
RAMP and RFREQ Value Setting
The laser should always have a forward current during
operation. This will prev ent the laser voltage from collapsing,
and ensure that the high frequency components reach the
junction without having to charge the junction capaci tance.
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 f or an output current close to a
sinusoidal wave form (refer to the proceeding performa nce
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 th e power
ground to avoid noise pick-up. These resistors should also
retur n to the EL6203'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.
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 high-
frequency noise of the EL6203's local environment from
propagating to the modulation source, and it will keep
parasitic capacitance at the pin minimized.
-
+
PIN
VREF
FIGURE 1. RAMP AND RFREQ PIN INTERFACE
EL6203
9
Supply Bypassing and Grounding
The resistance of bypass-capacitors an d the inductance of
bonding wires prev ent perf ect b ypass 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.
Also important is circuit-board layout. At the EL6203's
operating frequencies, even the ground plane is not low-
impedance. High frequency current will create voltage drops
in the ground plane. Figure 3 shows the output current loops .
For the pushing current loop, the current flows through the
bypass capacitor, into the EL6203 supply pin, out the IOUT
pin to the laser, and from th e 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.
Power Dissipation
With the high output drive capability, the EL6203 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.
The maximum power dissipation allowed in a package is
determined according to:
where
PDMAX = Maximum power dissipation in the package
TJMAX = Maximum junction temperature
TAMAX = Maximum ambient temperature
θJA = Thermal resistance of the package
The supply current of the EL6203 depends on the peak-to-
peak output current and the operating frequency which are
determ ined by resistors RAMP and RFREQ. The supply
current can be predicted approximately by the following
equation:
The power dissipation can be calculated from the following
equation:
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 de vice'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.
FIGURE 2. RECOMMENDED SUPPLY BYPASSING
+5VVS
L Series: 70Ω reactance at 300MHz
0.1µF
Chip
EL6203
GND
0.1µF
Chip
FIGURE 3. OUTPUT CURRENT LOOPS
Sinking Current Loop
Sourcing Current Loop
Supply
Bypass
Laser
Diode
RFREQ
RAMP
GND
PDMAX TJMAX - TAMAX
ΘJA
---------------------------------------------=
ISUP 31.25mA 1kΩ×
RAMP
-------------------------------------------30mA 1kΩ×
RFREQ
---------------------------------- 0.6mA++=
PDVSUP ISUP
×=
FIGURE 4.
0.6
0.5
0.4
0.3
0.2
0.1
00 255075100125150
Ambient Temperature (°C)
Power Dissipation (W)
85
Package Power Dissipation vs Ambient Temperature
JEDEC JESD51-3 Low Effective Thermal Conductivity Test Board
488mW
5-Pin SOT-23
θ
JA
=256°C/W
EL6203
10
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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. However, no responsibility is assumed by Intersil or its subsidiar ies for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license i s gr a nted b y imp lica tion or oth erw ise unde r any patent or patent rights of Intersi l or its subs idiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
FIGURE 5.
0.6
0.5
0.4
0.3
0.2
0.1
00 255075100125150
Ambient Temperature (°C)
Power Dissipation (W)
85
543mW
5-Pin SOT-23
θ
JA
=230°C/W
Package Power Dissipation vs Ambie nt Temperature
JEDEC JESD51-7 High Effective Thermal Conductivity Test Board
EL6203
