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MIC2937A/29371/29372
Micrel, Inc.
MIC2937A/29371/29372
750mA Low-Dropout Voltage Regulator
General Description
The MIC2937A family are "bulletproof" efficient voltage regulators with very low dropout voltage (typically 40mV at light loads and 300mV at 500mA), and very low quiescent current (160A typical). The quiescent current of the MIC2937A increases only slightly in dropout, thus prolonging battery life. Key MIC2937A features include protection against reversed battery, fold-back current limiting, and automotive "load dump" protection (60V positive transient). The MIC2937 is available in several configurations. The MIC2937A-xx devices are three pin fixed voltage regulators with 3.3V, 5V, and 12V outputs available. The MIC29371 is a fixed regulator offering logic compatible ON/OFF switching input and an error flag output. This flag may also be used as a power-on reset signal. A logic-compatible shutdown input is provided on the adjustable MIC29372, which enables the regulator to be switched on and off.
Features
* * * * * * * * * * * *
High output voltage accuracy Guaranteed 750mA output Low quiescent current Low dropout voltage Extremely tight load and line regulation Very low temperature coefficient Current and thermal limiting Input can withstand -20V reverse battery and +60V positive transients Error flag warns of output dropout Logic-controlled electronic shutdown Output programmable from 1.24V to 26V(MIC29372) Available in TO-220, TO-263, TO-220-5, and TO-263-5 packages. Battery Powered Equipment Cellular Telephones Laptop, Notebook, and Palmtop Computers PCMCIA VCC and VPP Regulation/Switching Bar Code Scanners Automotive Electronics SMPS Post-Regulator/ DC to DC Modules High Efficiency Linear Power Supplies
Applications
* * * * * * * *
Pin Configuration
INPUT GROUND OUTPUT TO-263 Package (MIC2937A-xxBU/WU) Five Lead Package Pin Functions: MIC29371 MIC29372 1) Error Adjust 2) Input Shutdown 3) Ground Ground 4) Output Input 5) Shutdown Output TO-263-5 Package (MIC29371/29372BU/WU)
123
12345
INPUT GROUND OUTPUT TO-220 Package (MIC2937A-xxBT/WT)
123
12345
TO-220-5 Package (MIC29371/29372BT/WT)
The TAB is Ground on the TO-220 and TO-263 packages.
Micrel, Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
May 2006
1
MIC2937A/29371/29372
MIC2937A/29371/29372
Micrel, Inc.
Ordering Information
Part Number Standard MIC2937A-3.3BU MIC2937A-3.3BT MIC2937A-5.0BU MIC2937A-5.0BT MIC2937A-12BU MIC2937A-12BT MIC29371-3.3BU MIC29371-3.3BT MIC29371-5.0BU MIC29371-5.0BT MIC29371-12BU MIC29371-12BT MIC29372BU MIC29372BT RoHS Compliant* MIC2937A-3.3WU MIC2937A-3.3WT MIC2937A-5.0WU MIC2937A-5.0WT MIC2937A-12WU MIC2937A-12WT MIC29371-3.3WU MIC29371-3.3WT MIC29371-5.0WU MIC29371-5.0WT MIC29371-12WU MIC29371-12WT MIC29372WU MIC29372WT Voltage 3.3V 3.3V 5.0V 5.0V 12V 12V 3.3V 3.3V 5.0V 5.0V 12V 12V ADJ ADJ Junction Temp. Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C Package TO-263-3 TO-220-3 TO-263-3 TO-220-3 TO-263-3 TO-220-3 TO-263-5 TO-220-5 TO-263-5 TO-220-5 TO-263-5 TO-220-5 TO-263-5 TO-220-5
* RoHS compliant with `high-melting solder' exemption.
MIC2937A/29371/29372
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MIC2937A/29371/29372
Micrel, Inc.
Operating Input Supply Voltage..................................................2V to 26V Adjust Input Voltage (Notes 9 and 10).................................-1.5V to +26V Shutdown Input Voltage .......................................................-0.3V to +30V Error Comparator Output Voltage.........................................-0.3V to +30V Across the full operating temperature, the minimum input voltage range for full output current is 4.3V to 26V. Output will remain in-regulation at lower output voltages and low current loads down to an input of 2V at 25C.
Absolute Maximum Ratings
Power Dissipation (Note 1)...............................................Internally Limited Lead Temperature (Soldering, 5 seconds).........................................260C Storage Temperature Range.............................................-65C to +150C Operating Junction Temperature Range ..........................-40C to +125C TO-220 JC .....................................................................................2.5C/W TO-263 JC .....................................................................................2.5C/W Input Supply Voltage..............................................................-20V to +60V
Electrical Characteristics
Limits in standard typeface are for TJ = 25C and limits in boldface apply over the full operating temperature range. Unless otherwise specified, VIN = VOUT + 1V, IL = 5mA, CL = 10F. The MIC29372 are programmed for a 5V output voltage, and VSHUTDOWN 0.6V (MIC29371-xx and MIC29372 only). Symbol VO Parameter Output Voltage Accuracy Conditions Variation from factory trimmed VOUT 5mA IL 500mA MIC2937A-12 and 29371-12 only: 5mA IL 500mA (Note 2) Output voltage > 10V VIN = VOUT + 1V to 26V IL = 5 to 500mA (Note 3) IL = 5mA IL = 100mA IL = 500mA IL = 750mA IGND Ground Pin Current (Note 5) IL = 5mA IL = 100mA IL = 500mA IL = 750mA VIN = 0.5V less than designed VOUT (VOUT 3.3V) IO = 5mA VOUT = 0V (Note 6) (Note 7) CL = 10F CL = 100F Min -1 -2 -2.5 -1.5 -3 -4 Typical Max 1 2 2.5 1.5 3 4 100 350 0.10 0.40 0.16 0.30 150 180 Units %
VO T VO VO VO VO VIN - VO
Output Voltage Temperature Coef. Line Regulation Load Regulation Dropout Voltage (Note 4)
20 80 0.03 0.04 80 200 240 300 420 370 160 1 8 15 200
ppm/C % % mV
Output voltage > 10V Output voltage > 10V
IGNDDO
ILIMIT VO PD en
Ground Pin Current at Dropout (Note 5) Current Limit Thermal Regulation Output Noise Voltage (10Hz to 100kHz)
600 750 250 300 2.5 3 13 16 25 500
A mA
A
1.1 0.05 400 260
1.5 2 0.2
A %/W V RMS
IL = 100mA
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MIC2937A/29371/29372
MIC2937A/29371/29372
Micrel, Inc.
Electrical Characteristics (Continued)
MIC29372
Parameter Reference Voltage Reference Voltage Adjust Pin Bias Current Reference Voltage Temperature Coefficient Adjust Pin Bias Current Temperature Coefficient Error Comparator Output Leakage Current Output Low Voltage Upper Threshold Voltage Lower Threshold Voltage Hysteresis Shutdown Input Input Logic Voltage Low (ON) (Note 7) (Note 8) Conditions Min 1.223 1.210 1.204 20 20 Typical 1.235 Max 1.247 1.260 1.266 40 60 Units V V max V nA ppm/C
0.1
nA/C
MIC29371
VOH = 26V VIN = 4.5V IOL = 250A (Note 9) (Note 9) (Note 9) 40 25 0.01 150 60 75 15 95 140 1.00 2.00 250 400 A mV mV mV mV
MIC29371/MIC29372
1.3 High (OFF) VSHUTDOWN = 2.4V VSHUTDOWN = 26V 2.0 30 0.7 V
Shutdown Pin Input Current
50 100 600 750 10 20
A
450 3
A A
Regulator Output Current in Shutdown
(Note 10)
MIC2937A/29371/29372
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MIC2937A/29371/29372
Micrel, Inc.
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its rated operating conditions. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ (MAX), the junction-to-ambient thermal resistance, JA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: P(MAX) = (TJ(MAX) - TA) / JA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. Note 2: Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. Note 3: Regulation is measured at constant junction temperature using low duty cycle pulse testing. Changes in output voltage due to heating effects are covered by the thermal regulation specification. Note 4: Dropout Voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V differential. At low values of programmed output voltage, the minimum input supply voltage of 4.3V over temperature must be taken into account. The MIC2937A operates down to 2V of input at reduced output current at 25C. Note 5: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current plus the ground pin current. Note 6: The MIC2937A family features fold-back current limiting. The short circuit (VOUT = 0V) current limit is less than the maximum current with normal output voltage. Note 7: Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 200mA load pulse at VIN = 20V (a 4W pulse) for T = 10ms. Note 8: VREF VOUT (VIN - 1 V), 4.3V VIN 26V, 5mA < IL 750 mA, TJ TJ MAX. Note 9: Comparator thresholds are expressed in terms of a voltage differential at the Adjust terminal below the nominal reference voltage measured at 6V input (for a 5V regulator). To express these thresholds in terms of output voltage change, multiply by the error amplifier gain = VOUT /VREF = (R1 + R2)/R2. For example, at a programmed output voltage of 5V, the Error output is guaranteed to go low when the output drops by 95 mV x 5V/1.235 V = 384 mV. Thresholds remain constant as a percent of VOUT as VOUT is varied, with the dropout warning occurring at typically 5% below nominal, 7.7% guaranteed. Note 10: Circuit of Figure 3 with R1 150k. VSHUTDOWN 2V and VIN 26V,VOUT = 0. Note 11: When used in dual supply systems where the regulator load is returned to a negative supply, the output voltage must be diode clamped to ground. Note 12: Maximum positive supply voltage of 60V must be of limited duration (< 100ms) and duty cycle ( 1%). The maximum continuous supply voltage is 26V.
Schematic Diagram
IN FEEDBACK
R18 20 k
Q15A
Q15B
Q24 Q25 Q26
OUT
Q9 Q3
R11 18 k
C1 20 pF
Q4 Q5
Q7
SENSE
Q8
Q16
Q6
Q1 10
R11 20.6 k
Q17
Q14
R17 12 k
R27
V TAP
R28
Q2
Q20
Q42
R1 20 k
R8 31.4 k
R10 150 k
Q22
R2 50 k
R5 180 k
Q13
R6 140 k
C2 40 pF
Q21
R15 100 k
R16 30 k
Q23
R9 27.8 k
Q40
Q41
R30 30 k
Q12
Q11
R12 110 k
R13 100 k
R14 350 k
Q18
R3 50 k
Q19
Q29
R17 10
R4 13 k
Q28
R21 8
50 k
Q37
Q30
Q31
R24 50 k
Q36
10 k
R22 150 k
R23 60 k
SHDN
ERROR
Q38
R26 60 k
Q34
R25 2.8 k
DENOTES CONNECTION ON MIC2937A-xx AND MIC29371-xx VERSIONS ONLY
Q39
GND
May 2006
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MIC2937A/29371/29372
MIC2937A/29371/29372
Micrel, Inc.
Typical Characteristics
Dropout Voltage vs. Output Current
DROPOUT VOLTAGE (mV)
500 DROPOUT VOLTAGE (mV) 400 300 200 100 0 0
700 600 500 400 300 200 100
Dropout Voltage vs. Temperature
OUTPUT VOLTAGE (V)
6 5 4 3 2 1 0 0
Dropout Characteristics
ILOAD = 5mA
ILOAD = 750mA
ILOAD = 750mA
200 400 600 800 OUTPUT CURRENT (mA)
0 -60 -30 0 30 60 90 120 150 TEMPERATURE C) (
1 2 3 4 5 INPUT VOLTAGE (V)
6
30 GROUND CURRENT (mA) 10
Ground Current vs. Output Current
GROUND CURRENT (A)
200 150 100 50 0
Ground Current vs. Supply Voltage
GROUND CURRENT (mA)
30 25 20 15 10 5 0 0
Ground Current vs. Supply Voltage
1
FIXED 5V VERSION ILOAD = 5mA
FIXED 5V ILOAD = 750mA 2 4 6 8 INPUT VOLTAGE (V) 10
0.1 1
10 100 1000 OUTPUT CURRENT (mA)
0
1
2 3 4 5 67 SUPPLY VOLTAGE (V)
8
0.25 GROUND CURRENT (mA) 0.20 0.15 0.10 0.05
Ground Current vs. Temperature
GROUND CURRENT (mA)
ILOAD = 5mA
0.00 -60 -30 0 30 60 90 120 150 TEMPERATURE C) (
2.0 1.8 1.6 1.4 ILOAD = 100mA 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -60 -30 0 30 60 90 120 150 TEMPERATURE C) (
Ground Current vs. Temperature
30 GROUND CURRENT (mA) 25 20 15 10 5
Ground Current vs. Temperature
ILOAD = 750mA
0 -60 -30 0 30 60 90 120 150 TEMPERATURE C) (
3.40 3.38 3.36 3.34 3.32 3.30 3.28 3.26 3.24 3.22 3.20 -60 -30 0 30 60 90 120 150 TEMPERATURE C) (
Fixed 3.3V Output Voltage vs. Temperature
1.4 1.2 CURRENT (A) 1.0 0.8 0.6 0.4 0.2
Short Circuit and Maximum Current vs. Temperature
GROUND CURRENT (A) VOUT = VNOMINAL - 0.5V
500 400 300 200 100 0
Ground Current vs. Input Voltage
RLOAD = 100
OUTPUT VOLTAGE (V)
VOUT = 0V
FIXED 5V VERSION
0.0 -60 -30 0 30 60 90 120 150 TEMPERATURE C) (
-100 -30 -20 -10 0 10 20 INPUT VOLTAGE (V)
30
MIC2937A/29371/29372
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May 2006
MIC2937A/29371/29372
Micrel, Inc.
OUTPUT (mA) OUTPUT (mV)
ENABLE CURRENT (A)
100 75 50 25
150 0 -150
COUT = 10 F
OUTPUT (mA) OUTPUT (mV)
125
MIC29371/2 Shutdown Current vs. Temperaure
300
Load Transient
200 100 0 -100
Load Transeint
COUT = 100 F
VEN = 5V
VEN = 2V
0 -60 -30 0 30 60 90 120 150 TEMPERATURE C) (
-300 1000 750 500 5mA 250 0 -250 -5
0 5 TIME (ms)
10
-200 1000 750 500 5mA 250 0 -250 -5
0 5 TIME (ms)
10
OUTPUT (mV)
ADJUST PIN CURRENT (nA)
40 30 20 10 ILOAD = 1mA
20 0
COUT = 10 F IL = 5mA
OUTPUT (mV)
50
MIC29372/3 Adjust Pin Current vs. Temperature
40
Line Transient
20 10 0
Line Transient
COUT = 100 F IL = 5mA
-20 -40 10 8 6 4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 TIME (ms)
-10 10 8 6 4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 TIME (ms)
0 -60 -30 0 30 60 90 120 150 TEMPERATURE C) (
10
Output Impedance vs. Frequency
OUTPUT IMPEDANCE ()
1
0.1 ILOAD = 10mA 0.01
10x100
1x103
100x100
100x103
1x100
10x103
FREQUENCY (Hz)
May 2006
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1x106
INPUT (V)
INPUT (V)
MIC2937A/29371/29372
MIC2937A/29371/29372
Micrel, Inc.
Applications Information
External Capacitors
A 10F (or greater) capacitor is required between the MIC2937A output and ground to prevent oscillations due to instability. Most types of tantalum or aluminum electrolytics will be adequate; film types will work, but are costly and therefore not recommended. Many aluminum electrolytics have electrolytes that freeze at about -30C, so solid tantalums are recommended for operation below -25C. The important parameters of the capacitor are an effective series resistance of about 5 or less and a resonant frequency above 500kHz. The value of this capacitor may be increased without limit. At lower values of output current, less output capacitance is required for output stability. The capacitor can be reduced to 0.5F for current below 10mA or 0.15F for currents below 1 mA. Adjusting the MIC29372 to voltages below 5V runs the error amplifier at lower gains so that more output capacitance is needed. For the worst-case situation of a 750mA load at 1.23V output (Output shorted to Adjust) a 22F (or greater) capacitor should be used. The MIC2937A/29371 will remain in regulation with a minimum load of 5mA. When setting the output voltage of the MIC29372 version with external resistors, the current through these resistors may be included as a portion of the minimum load. A 0.1F capacitor should be placed from the input to ground if there is more than 10 inches of wire between the input and the AC filter capacitor or if a battery is used as the input. The error comparator has an NPN open-collector output which requires an external pull-up resistor. Depending on system requirements, this resistor may be returned to the 5V output or some other supply voltage. In determining a value for this resistor, note that while the output is rated to sink 250A, this sink current adds to battery drain in a low battery condition. Suggested values range from 100k to 1M. The resistor is not required if this output is unused.
Programming the Output Voltage (MIC29372)
The MIC29372 may programmed for any output voltage between its 1.235V reference and its 26V maximum rating. An external pair of resistors is required, as shown in Figure 3. The complete equation for the output voltage is VOUT = VREF x { 1 + R1/R2 } - |IFB| R1 where VREF is the nominal 1.235 reference voltage and IFB is the Adjust pin bias current, nominally 20nA. The minimum recommended load current of 1A forces an upper limit of 1.2M on the value of R2, if the regulator must work with no load (a condition often found in CMOS in standby), IFB will produce a -2% typical error in VOUT which may be eliminated at room temperature by trimming R1. For better accuracy, choosing R2 = 100k reduces this error to 0.17% while increasing the resistor program current to 12A. Since the MIC29372 typically draws 100A at no load with SHUTDOWN open-circuited, this is a negligible addition.
Error Detection Comparator Output (MIC29371)
A logic low output will be produced by the comparator whenever the MIC29371 output falls out of regulation by more than approximately 5%. This figure is the comparator's built-in offset of about 75mV divided by the 1.235V reference voltage. (Refer to the block diagram on Page 1). This trip level remains "5% below normal" regardless of the programmed output voltage of the MIC29371. For example, the error flag trip level is typically 4.75V for a 5V output or 11.4V for a 12V output. The out of regulation condition may be due either to low input voltage,extremely high input voltage, current limiting, or thermal limiting. Figure 1 is a timing diagram depicting the ERROR signal and the regulated output voltage as the MIC29371 input is ramped up and down. The ERROR signal becomes valid (low) at about 1.3V input. It goes high at about 5V input (the input voltage at which VOUT = 4.75). Since the MIC29371's dropout voltage is load-dependent (see curve in Typical Performance Characteristics), the input voltage trip point (about 5V) will vary with the load current. The output voltage trip point (approximately 4.75V) does not vary with load.
Reducing Output Noise
In reference applications it may be advantageous to reduce the AC noise present at the output. One method is to reduce the regulator bandwidth by increasing the size of the output capacitor. This is relatively inefficient, as increasing the capacitor from 1F to 220F only decreases the noise from 430V to 160VRMS for a 100kHz bandwidth at 5V output. Noise can be reduced by a factor of four with the adjustable regulators
OUTPUT VOLTAGE
4.75V
ERROR NOT* VALID INPUT VOLTAGE 5V 1.3V
NOT* VALID
* SEE APPLICATIONS INFORMATION
Figure 1. ERROR Output Timing
MIC2937A/29371/29372
8
May 2006
MIC2937A/29371/29372 with a bypass capacitor across R1, since it reduces the high frequency gain from 4 to unity. Pick
CBYPASS 1 2 R1 * 200 Hz
Micrel, Inc.
Automotive Applications
The MIC2937A is ideally suited for automotive applications for a variety of reasons. It will operate over a wide range of input voltages with very low dropout voltages (40mV at light loads), and very low quiescent currents (100A typical). These features are necessary for use in battery powered systems, such as automobiles. It is a "bulletproof" device with the ability to survive both reverse battery (negative transients up to 20V below ground), and load dump (positive transients up to 60V) conditions. A wide operating temperature range with low temperature coefficients is yet another reason to use these versatile regulators in automotive designs.
or about 0.01F. When doing this, the output capacitor must be increased to 10F to maintain stability. These changes reduce the output noise from 430V to 100VRMS for a 100 kHz bandwidth at 5V output. With the bypass capacitor added, noise no longer scales with output voltage so that improvements are more dramatic at higher output voltages.
Typical Applications
VIN +VIN VOUT + GND
VOUT = 5V
SHUTDOWN INPUT
OFF
VIN VOUT
VOUT 1.2V
26V
SHUTDOWN GND ADJUST 1.23V
10F
ON
R1 .01 F
10F
V REF R VOUT = VREF x (1 + 1 ) R2
R2
Figure 2. MIC2937A-5.0 Fixed +5V Regulator
Figure 3. MIC29372 Adjustable Regulator
+5V to +7V
+VIN
+V IN V CC OUT VOUT SHUTDOWN
OFF ON
VIN VOUT
VOUT VIN
SHUTDOWN INPUT
GND
ADJUST
100pF
300k 1%
+
10F
GND
ADJUST
5V 3.3V Input 0 1 Output 3.3V 5.0V
470 k
220k 1% 2N2222
180k 1%
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV, DEPENDING ON LOAD CURRENT.
SHUTDOWN PIN LOW= ENABLE OUTPUT. Q1 ON = 3.3V, Q1 OFF = 5.0V.
Figure 4. MIC29372 Wide Input Voltage Range Current Limiter
Figure 5. MIC29372 5.0V or 3.3V Selectable Regulator with Shutdown.
May 2006
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MIC2937A/29371/29372
MIC2937A/29371/29372
Micrel, Inc.
Package Information
3-Pin TO-263 (U)
3-Pin TO-220 (T)
MIC2937A/29371/29372
10
May 2006
MIC2937A/29371/29372
Micrel, Inc.
4
1
2
1
3
1 2 3 4
1
5-Pin TO-263 (U)
5-Pin TO-220 (T)
May 2006
11
MIC2937A/29371/29372
MIC2937A/29371/29372
Micrel, Inc.
MICREL INC.
TEL
+ 1 (408) 944-0800
2180 FORTUNE DRIVE
FAX
+ 1 (408) 474-1000
SAN JOSE, CA 95131
WEB
http://www.micrel.com
USA
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 1999 Micrel, Inc.
MIC2937A/29371/29372
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May 2006

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