MICREL MIC2253

MIC2253
3.5A 1MHz High Efficiency
Boost Regulator with OVP and Softstart
General Description
Features
The MIC2253 is a high power density 1MHz PWM DC/DC
boost regulator. The 3.5A minimum switch current limit
combined with a 1MHz switching frequency allows the
MIC2253 to use smaller inductors and deliver high power
in a tiny solution size.
The 2.5V to 10V input voltage range of MIC2253 allows
direct operation from 1 and 2 cell Li-ion as well as 3 to 4
cell NiCad, NiMH, Alkaline or lithium batteries. Maximum
battery life is assured with a low 0.1µA shutdown current.
The MIC2253 is available in a low profile 12-pin 3mm x
3mm MLF© package. To prevent a high inrush current, a
minimum 1ms soft-start period is set by default and the
MIC2253 has the ability to extend the soft-start period with
an external capacitor.
Datasheet and support documentation can be found on
Micrel’s web site at: www.micrel.com.
•
•
•
•
•
•
•
•
•
•
•
•
•
3.5A minimum switch current
1.245V ± 3% feedback voltage
2.5V to 10V input voltage
Output over-voltage protection (OVP)
Externally programmable soft-start
Output voltage up to 30V (max)
Fixed 1MHz operation
<1% line regulation
0.1µA shutdown current
Over temperature protection
Under-voltage lockout (UVLO)
12-pin 3mm x 3mm leadless MLF® package
–40°C to +125°C junction temperature range
Applications
• Mobile handsets
• Portable media/MP3 players
• Portable navigation devices (GPS)
• WiFi/WiMax/WiBro modules
• Digital Cameras
• Wireless LAN cards
• USB powered devices
• Portable applications
___________________________________________________________________________________________________________
Typical Application
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
February 2010
M9999-021710-B
Micrel, Inc.
MIC2253
Ordering Information
Part Number
MIC2253-06YML
Marking
Code(2)
06
2253
OVP
Junction Temp. Range
Package
Lead Finish
6V
–40° to +125°C
12-Pin 3x3 MLF®
Pb-Free
®
Note: MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Pin Configuration
®
12-Pin 3mm x 3mm MLF (ML)
(Top View)
Pin Description
Pin Number
Pin Name
1
NC
No connect. Not internally connected.
Pin Function
2
SS
Soft start (Input). Connect a capacitor to GND to slowly turn on the device. The
higher the capacitance, the longer the turn-on time.
3
FB
Feedback (Input): Output voltage sense node. Connect external resistors to set
the output voltage. Nominal feedback voltage is 1.245V.
4
AGND
Analog Ground
5,6
PGND
Power Ground
7,8
SW
Switch Node: Internal power BIPOLAR collector.
9
OVP
Over-Voltage Protection (OVP): Connect to the output voltage to clamp the
maximum output voltage. A resistor divider from this pin to ground could be
used to raise the OVP level beyond 6V (max).
10
VIN
Supply (Input): 2.5V to 10V for internal circuitry.
11
EN
Enable (Input): Applying 1.5V or greater enables the regulator. Applying a
voltage of 0.4V or less disables the MIC2253. Do not leave floating.
12
COMP
Compensation pin (Input): Add external R and C to GND to stabilize the
converter.
EP
HS Pad
Exposed Heat-Sink pad.
February 2010
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Micrel, Inc.
MIC2253
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) .......................................................12V
Switch Voltage (VSW)....................................... –0.3V to 34V
Enable Voltage (VEN)....................................... –0.3V to 12V
FB Voltage (VFB)...............................................................6V
Switch Current (ISW) ..................................Internally Limited
Ambient Storage Temperature (Ts) ...........–65°C to +150°C
ESD Rating(3) .................................................................. 2kV
Supply Voltage (VIN).......................................... 2.5V to 10V
Enable Voltage (VEN).............................................. 0V to VIN
Junction Temperature (TJ) ........................ –40°C to +125°C
Package Thermal Impedance
3mm x 3mm MLF-12 (θJA) .................................60°C/W
Electrical Characteristics(4)
TA = 25°C; VIN = VEN = 3.6V; unless otherwise noted. Bold values indicate –40°C≤ TJ ≤ +125°C.
Symbol
Parameter
Condition
Min
Typ
VIN
Supply Voltage Range
VUVLO
Under-Voltage Lockout
1.8
2.1
2.4
V
VOVP
Over-Voltage Protection
5.25
5.6
6.3
V
2.5
Max
Units
10
V
IVIN
Quiescent Current
VFB >1.245V, Not Switching
15
23
mA
ISD
Shutdown Current
VEN = 0V(5)
0.1
1
µA
VFB
Feedback Voltage
1.245
1.283
V
IFB
Feedback Input Current
VFB = 1.245V
Line Regulation
3.0V ≤ VIN ≤ 4.5V
1.208
-450
nA
0.5
%
DMIN
Minimum Duty Cycle
10
%
DMAX
Maximum Duty Cycle
90
%
ISW
Switch Current Limit
VIN = 3.6V
VSW
Switch Saturation Voltage
VIN = 3.6V, ISW = 3.5A
ISW
Switch Leakage Current
VEN
Enable Threshold
IEN
Enable Pin Current
fSW
Oscillator Frequency
ISS
Soft start
TJ
Over-Temperature Threshold
Shutdown
3.5
VEN = 0V, VSW = 10V
TURN ON
4.75
8
A
350
500
mV
0.01
10
µA
1.5
TURN OFF
0.4
VEN = 10V
0.8
VSS = 0V
Hysteresis
V
20
40
µA
1
1.2
MHz
30
µA
150
°C
10
°C
Notes:
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 operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(Max), the
junction-to-ambient thermal resistance, θ JA, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive die
temperature, and the regulator will go into thermal shutdown.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human Body Model, 1.5kΩ in series with 100pF.
4. Specification for packaged product only.
5. ISD = IVIN
February 2010
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Micrel, Inc.
MIC2253
Typical Characteristics
V IN =3.3V
80
V IN =3V
60
V IN =2.5V
50
40
30
20
80
80
V IN =4.5V
V IN =2.5V
L = 2.2µH
C = 22µF
TA = 25°C
30
600
1200
1800
2400
OUTPUT CURR EN T (mA)
0
L = 2.2µH
C = 22µF
TA = 25°C
40
30
0
600
1200
1800
2400
OUTPU T CU RRENT (mA)
200 400 600 800 1000 1200
OUTPUT C URRENT (mA)
Quiescent Current
vs. T emperature
Efficiency V OUT =15.0V
17.0
90
V IN =3.3V
50
40
20
0
V IN =4.2V
60
50
0
V IN =5V
70
V IN =3.6V
60
L = 2.2µH
C = 22µF
TA = 25°C
10
90
70
EFFIC IEN CY (%)
EFFICIENC Y (%)
70
90
EFFICIENCY (%)
100
90
Efficiency V OUT =12.0V
Efficiency V OUT =5.0V
Efficiency V OUT = 3.8V
Quiescent Current
vs. Input Voltage
17.0
70
QUIESCENT CURRENT ( mA)
EFFICIENCY (%)
80
V IN =5V
60
V IN =3.3V
V IN =4.2V
50
L = 2.2µH
C = 22µF
TA = 25°C
40
30
0
16.0
15.5
15.0
14.5
14.0
13.5
13.0
V IN = 3.6V
12.5
V F B = 2.5V
Not Switching
-40 -20
0
20
40
60
13.0
12.0
V F B = 2.5V
Not Switching
2.5
TEMPERATURE(°C)
4.0
5.5
7.0
8.5
10.0
IN PUT VOLTAGE (V)
Feedback Voltage
vs. T emperature
1200
1.30
1.29
1100
1200
1.28
FEEDBAC K VOLTA GE (V)
FREQUENCY ( kHz)
1300
1.27
1000
1100
1000
900
800
V OU T = 12V
700
IOU T = 300mA
L = 2.2µH
C = 22µF
600
4.0
5.5
7.0
8.5
INPUT VOLTAGE (V)
1.25
900
1.24
1.23
V OU T = 5V
800
V IN = 3.6V
Load = 200mA
700
500
2.5
1.26
V OU T = 5V
1.21
V IN = 3.6V
Load = 200mA
1.20
-40 -20
10.0
1.22
0
20 40 60 80 100 120
-40 -20
TEMPERATURE (°C)
Load Regulation
5.0
12.4
4.9
5.06
12.3
4.8
OUTPUT VOLTA GE (V)
12.5
5.08
12.2
12.1
5.02
12.0
5.00
11.9
4.98
4.96
V OU T = 5V
L = 2.2µH
C = 22µF
TA = 25°C
4.94
4.92
4.90
0
400
800
1200
1600
OUTPUT CU RRENT (mA)
February 2010
V OU T = 12V
L = 2.2µH
C = 22µF
TA = 25°C
Load = 20mA
11.8
11.7
11.6
20 40 60
80 100 120
Current Limit
vs. Input Voltage
Line Regulation
5.10
5.04
0
TEMPERATUR E (°C)
SW CURRENT LIMIT (A)
FREQUENCY (kHz)
14.0
80 100 120
1400
OUTPUT VOLTAGE (V)
15.0
Frequency
vs. T emperature
Frequency
vs. Input Voltage
1500
16.0
11.0
12.0
100 200 300 400 500 600 700
OUTPUT CU RRENT (mA)
QUIESCENT CURRENT (mA)
16.5
4.7
4.6
4.5
4.4
4.3
V OU T = 12V
L = 2.2µH
C = 22µF
TA = 25°C
4.2
4.1
11.5
4.0
2.5
4.0
5.5
7.0
8.5
INPUT VOLTAGE (V)
4
10.0
2.5
4.0
5.5
7.0
8.5
INPUT VOLTAGE (V)
10.0
M9999-021710-B
Micrel, Inc.
MIC2253
Typical Characteristics (Continued)
Saturation Voltage
vs. Switch Current
1.40
400
1.38
350
1.36
ENABLE THRESHOLD (V)
SATURATION VOLTAGE (mV)
450
300
250
200
150
100
V IN = 2.5V
50
Enable T hreshold
vs. Input Voltage
TA = 25°C
0
1.34
1.32
1.30
1.28
1.26
V OU T = 12V
1.24
IOU T = 20mA
L = 2.2µH
C = 22µF
1.22
1.20
0.0
0.5 1.0 1.5 2.0 2.5 3.0
SWITCH CURRENT (A)
February 2010
3.5
2.5
4.0
5.5
7.0
8.5
10.0
INPUT VOLTAGE (V)
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Micrel, Inc.
MIC2253
Functional Characteristics
February 2010
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Micrel, Inc.
MIC2253
Functional Diagram
The gm error amplifier measures the feedback voltage
through the external resistor and amplifies the error
between the detected voltage signal from the feedback
and the internal reference voltage. The output of the gm
error amplifier provides the voltage loop signal that is fed
to the other input of the PWM comparator. When the
current loop signal exceeds the voltage loop signal the
PWM comparator turns off the power transistor. The next
oscillator/clock period initiates the next switching cycle,
maintaining the constant frequency current-mode PWM
control. The enable pin shuts down the output switching
and disables control circuitry to reduce input current-toleakage levels. Enable pin input current is approximately
zero, at zero volts.
Functional Description
The MIC2253 is a constant frequency, pulse-widthmodulated (PWM) peak current-mode step-up regulator.
The device’s simplified control scheme is illustrated in the
block diagram above. A reference voltage is fed into the
PWM engine where the duty cycle output of the constant
frequency PWM engine is computed from the error, or
difference, between the REF and FB voltages. The PWM
engine encompasses the necessary circuit blocks to
implement a current-mode boost switching power supply.
The necessary circuit blocks include, but are not limited to,
an oscillator/ramp generator, slope compensation ramp
generator, gm error amplifier, current amplifier, PWM
comparator, and drive logic for the internal 3.5A bipolar
power transistor.
Inside the PWM engine, the oscillator functions as a trigger
for the PWM comparator that turns on the bipolar power
transistor and resets the slope compensation ramp
generator. The current amplifier is used to measure the
power transistor’s current by amplifying the voltage signal
from the sense resistor connected to the emitter of the
bipolar power transistor. The output of the current amplifier
is summed with the output of the slope compensation ramp
generator where the result is connected to one of the inputs
of the PWM comparator.
February 2010
DC-to-DC PWM Boost Conversion
The MIC2253 is a constant-frequency boost converter. It
can convert a low DC input voltage to a high DC output
voltage. Figure 1 shows a typical circuit. Boost regulation
is achieved by turning on an internal switch, which draws
current through the inductor. When the switch turns off,
the inductor’s magnetic field collapses. This causes the
current to be discharged into the output capacitor
through an external Schottky diode. The Functional
Characteristics show Input Voltage ripple, Output
Voltage ripple, SW Voltage, and Inductor Current for
300mA load current. Regulation is achieved by
modulating the pulse width i.e., pulse-width modulation
(PWM).
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Micrel, Inc.
MIC2253
Over-Voltage Protection (OVP)
The MIC2253 provides a fixed 5.6V overvoltage
protection. The overvoltage functionality will clamp the
output voltage to a safe level in the event that a fault
condition causes the output voltage to increase beyond
control. To ensure the highest level of protection, the
MIC2253 OVP pin will shut the switch off when an
overvoltage condition is detected, saving itself, the
output capacitor, and downstream devices from damage.
Two external resistors can be used to change the OVP
from the range of 6V to 30V. Be careful not to exceed
the 30V rating of the switch. The OVP feature may be
disabled by grounding the OVP pin.
The OVP pin is connected internally to a reference
voltage via a voltage divider circuit. For a 5.6V OVP
setting, connect the OVP pin directly to the output
voltage as shown in Figure 1. To increase the OVP
voltage above 5.6V, an external parallel resistor network
can be configured, as shown in Figure 2, with the
following equation:
Figure 1. Typical Application Circuit
Duty Cycle Considerations
Duty cycle refers to the switch on-to-off time ratio and can
be calculated as follows for a boost regulator:
D =1
VIN
VOUT
VOVP = 1.245 ×
However at light loads, the inductor will completely
discharge before the end of a switching cycle. The current
in the inductor reaches zero before the end of the switching
cycle. This is known as discontinuous conduction mode
(DCM). DCM occurs when:
IOUT <
67k × (R1 + R2)
15k × R2
VIN IPEAK
×
VOUT
2
where
IPEAK <
(VOUT - VIN ) ⎛ VIN
× ⎜⎜
L×f
⎝ VOUT
⎞
⎟⎟
⎠
In DCM, the duty cycle is smaller than in continuous
conduction mode. In DCM the duty cycle is given by:
D=
Figure 2. Adjustable OVP Circuit
f × 2 × L × IOUT × (VOUT − VIN )
Note:
VIN
1. The maximum value of R2 is 30kΩ.
The duty cycle required for voltage conversion should be
less than the maximum duty cycle of 90%. Also, in light load
conditions where the input voltage is close to the output
voltage, the minimum duty cycle can cause pulse skipping.
This is due to the energy stored in the inductor causing the
output to slightly overshoot the regulated output voltage.
During the next cycle, the error amplifier detects the output
as being high and skips the following pulse. This effect can
be reduced by increasing the minimum load or by
increasing the inductor value. Increasing the inductor value
also reduces the peak current. Minimum duty cycle is
typically 10%.
February 2010
Soft Start Functionality
The soft start time is dependant up on both CSS and the
comp capacitor values. CCOMP is fixed for stable
operation (typically 10nF); therefore, if any increases in
soft start are desired, this should be done using the CSS
capacitor. The approximate total startup time is given by:
TSS = 1ms + 85k × CSS
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M9999-021710-B
Micrel, Inc.
MIC2253
inductor current and the maximum reverse voltage is
rated greater than the output voltage.
Component Selection
Inductor
The MIC2253 is designed to work with a 2.2µH inductor.
This is due to the unavoidable “right half plane zero” effect
for the continuous current boost converter topology. The
frequency at which the right half plane zero occurs can be
calculated as follows:
Input Capacitor
A minimum 2.2µF ceramic capacitor with an X5R or X7R
dielectric is recommended for designing with the
MIC2253. Increasing input capacitance will improve
performance and greater noise immunity on the source.
The input capacitor should be as close as possible to the
inductor and the MIC2253, with short traces for good
noise performance.
2
frhpz =
VOUT
VIN
× L × IOUT × 2π
The right half plane zero has the undesirable effect of
increasing gain, while decreasing phase. This requires that
the loop gain is rolled off before this has significant effect on
the total loop response. This can be accomplished by either
reducing inductance (increasing RHPZ frequency) or
increasing the output capacitor value (decreasing loop
gain).
Compensation
The comp pin is connected to the output of the voltage
error amplifier. The voltage error amplifier is a
transconductance amplifier. Adding a series RC-toground adds a zero at:
fzero =
Output Capacitor
Output capacitor selection is a trade-off between
performance, size, and cost. Increasing output capacitance
will lead to an improved transient response, but also an
increase in size and cost. X5R or X7R dielectric ceramic
capacitors are recommended for designs with the MIC2253.
The output capacitor sets the frequency of the dominant
pole and zero in the power stage. The zero is given by:
fz =
The resistor should be set to approximately 600Ω. The
capacitor typically ranges from 10nF to 100nF.
Adding an optional capacitor from comp pin-to-ground
adds a pole at approximately:
fpole =
C × R esr × 2π
Feedback Resistors
The feedback pin (FB) provides the control path to the
control the output. The FB pin is used to compare the
output to an internal reference. Output voltages are
adjusted by selecting the appropriate feedback network
values. The desired output voltage can be calculated as
follows:
IOUT
C × VOUT × 2 × π
⎛R
⎞
VOUT = VREF ⋅ ⎜⎜ 1 + 1⎟⎟
R
⎝ 2
⎠
Diode Selection
The MIC2253 requires an external diode for operation. A
Schottky diode is recommended for most applications due
to their lower forward voltage drop and reverse recovery
time. Ensure the diode selected can deliver the peak
February 2010
1
2πR 2 C 3
This capacitor typically is 100pF. Generally, an RC to
ground is all that is needed. The RC should be placed as
close as possible to the compensation pin. The capacitor
should be a ceramic with a X5R, X7R, or COG dielectric.
Refer to the MIC2253 evaluation board document for
component location.
1
For ceramic capacitors, the ESR is very small. This puts the
zero at a very high frequency where it can be ignored.
Fortunately, the MIC2253 is current mode in operation
which reduces the need for this output capacitor zero when
compensating the feedback loop.
The frequency of the pole caused by the output capacitor is
given by:
fp =
1
2πR 2 C 4
where VREF is equal to 1.245V.
9
M9999-021710-B
Micrel, Inc.
MIC2253
MIC2253 Sample Schematic
February 2010
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M9999-021710-B
Micrel, Inc.
MIC2253
Bill of Materials
Item
C1
Part Number
C1608X5R1C225K
GRM188R61C225KE15
CL10A225K08NNN
C2
C1608X7R1H104K/10
L1
Samsung
Capacitor, 0.1µF, 16V, X7R, 0603 size
C1608C0G1H101J
TDK
Capacitor, 100pF, 50V, C0G, 0603 size
Murata
Capacitor, 100pF, 50V, C0G, 0603 size
Samsung
Capacitor, 100pF, 50V, C0G, 0603 size
AVX(4)
Capacitor, 100pF, 50V, C0G, 0603 size
C1608X5R1H103K
TDK
Capacitor, 10nF, 50V, X5R, 0603 size
CL10B103KB8NNN
Samsung
Capacitor, 10nF, 50V, X5R, 0603 size
06035C103KA12A
AVX
Capacitor, 10nF, 50V, X5R, 0603 size
CL21A226MPCLRNC
Samsung
Taiyo Yuden
Schottky Diode, 3A, 20V
SK34
MCC
Schottky Diode, 3A, 40V
LTF5022T-2R2N3R2
TDK
Inductor, 2.2µH, 3.4A, 5.2 x 5.0 x 2.2mm
RLF7030T-2R2M
TDK
Inductor, 2,2µH, 5.4A, 6.8 x 7.3 x 3.2mm
CRCW06031002FRTI
1
1
(7)
(8)
Vishay
1
Capacitor, 22µF, 10V, X5R, 0805 size
MCC(6)
Coilcraft
1
Capacitor, 22µF, 10V, X5R, 0805 size
(5)
SK32
MOS6020-222ML
R1
Capacitor, 2.2µF, 16V, X5R, 0603 size
CL10B104KB8NNN
LMK212BJ226MG-T
D1
Samsung
1
Capacitor, 2.2µF, 16V, X5R, 0603 size
(3)
Capacitor, 0.1µF, 16V, X7R, 0603 size
06035A101AT2A
Qty.
Capacitor, 2.2µF, 16V, X5R, 0603 size
Murata(2)
Murata
CL10C101JB8NNN
C5
Description
Capacitor, 0.1µF, 16V, X7R, 0603 size
GRM1885C1H101JA01
C4
TDK
(1)
TDK
GRM188R71H104KA93
C3
Manufacturer
1
1
Inductor, 2.2µH, 3.56A, 6.0 x 7.1 x 2.4mm
Resistor, 10kΩ, 1%, 1/16W, 0603 size
1
R2
CRCW06036200FRTI
Vishay
Resistor, 620Ω, 1%, 1/16W, 0603 size
1
R4
CRCW06031003FRTI
Vishay
Resistor, 100kΩ, 1%, 1/16W, 0603 size
1
R5
CRCW06033092FRTI
Vishay
Resistor, 30.9kΩ, 1%, 1/16W, 0603 size
1
1MHz High Efficiency Boost Regulator with OVP and
Softstart
1
U1
MIC2253-06YML
Micrel, Inc.
(9)
Notes:
1. TDK: www.tdk.com
2. Murata: www.murata.com
3. Samsung: www.sem.samsung.com
4. AVX: www.avx.com
5. Taiyo Yuden: www.t-yuden.com
6. MCC: www.mccsemi.com
7. Coilcraft: www.coilcraft.com
8. Vishay: www.vishay.com
9. Micrel, Inc.: www.micrel.com
February 2010
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Micrel, Inc.
MIC2253
Recommended Layout
Top Layout
Bottom Layout
February 2010
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Micrel, Inc.
MIC2253
Package Information
12-Pin 3mm x 3mm MLF® (ML)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The 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.
© 2009 Micrel, Incorporated.
February 2010
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