MAXIM MAX4238, MAX4239 User Manual

General Description

The MAX4238/MAX4239 are low-noise, low-drift, ultra­high precision amplifiers that offer near-zero DC offset
and drift through the use of patented autocorrelating
zeroing techniques. This method constantly measures
and compensates the input offset, eliminating drift over
time and temperature and the effect of 1/f noise. Both
devices feature rail-to-rail outputs, operate from a single

2.7V to 5.5V supply, and consume only 600µA. An active­low shutdown mode decreases supply current to 0.1µA.

The MAX4238 is unity-gain stable with a gain-band­width product of 1MHz, while the decompensated
MAX4239 is stable with A

V

≥ 10V/V and a GBWP of

6.5MHz. The MAX4238/MAX4239 are available in 8-pin
narrow SO, 6-pin TDFN and SOT23 packages.

Applications

Thermocouples

Strain Gauges

Electronic Scales

Medical Instrumentation

Instrumentation Amplifiers

Features

o Ultra-Low, 0.1µV Offset Voltage

2.0µV (max) at +25°C

2.5µV (max) at -40°C to +85°C

3.5µV (max) at -40°C to +125°C

o Low 10nV/°C Drift

o Specified over the -40°C to +125°C Automotive

Temperature Range

o Low Noise: 1.5µV

P-P

from DC to 10Hz

o 150dB A

VOL

, 140dB PSRR, 140dB CMRR

o High Gain-Bandwidth Product

1MHz (MAX4238)

6.5MHz (MAX4239)

o 0.1µA Shutdown Mode

o Rail-to-Rail Output (R

L

= 1kΩ)

o Low 600µA Supply Current

o Ground-Sensing Input

o Single 2.7V to 5.5V Supply Voltage Range

o Available in a Space-Saving 6-Pin SOT23 and

TDFN Packages

MAX4238/MAX4239

Ultra-Low Offset/Drift, Low-Noise,

Precision SOT23 Amplifiers

________________________________________________________________

Maxim Integrated Products

1

Typical Application Circuit

19-2424; Rev 3; 8/11

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.

Pin Configurations appear at end of data sheet.

Note: All devices are specified over the -40°C to +125°C oper-

ating temperature range.

+

Denotes a lead(Pb)-free/RoHS-compliant package.

*

EP = Exposed paddle.

/V denotes an automotive-qualified part.

Ordering Information

Selector Guide

5V

18kΩ

18kΩ

AV = 100

MAX4238/

ADC

AIN

MAX4239

360Ω

STRAIN GAUGE

PART PIN-PACKAGE TOP MARK

MAX4238AUT-T 6 SOT23 AAZZ

MAX4238AUT/V+T 6 SOT23 —

MAX4238ASA 8 SO —

MAX4238ATT+T 6 TDFN-EP* +ANG

MAX4239AUT-T 6 SOT23 ABAA

MAX4239AUT/V+T 6 SOT23 —

MAX4239ASA 8 SO —

MAX4239ATT+T 6 TDFN-EP* +ANH

PART

MAX4238 1V/V 1
MAX4239 10V/V 6.5

MINIMUM STABLE

GAIN

GAIN

BANDWIDTH

(MHz)

MAX4238/MAX4239

Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(2.7V ≤ VCC≤ 5.5V, VCM= V

GND

= 0V, V

OUT

= VCC/2, RL= 10kΩ connected to VCC/2, SHDN = VCC, TA= +25°C,

unless otherwise noted.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

Power-Supply Voltage (VCCto GND).......................................6V

All Other Pins ................................(V

GND

- 0.3V) to (VCC+ 0.3V)

Output Short-Circuit Duration

(OUT shorted to V

CC

or GND) ...............................Continuous

Continuous Power Dissipation (T

A

= +70°C)

6-Pin Plastic SOT23

(derate 9.1mW/°C above +70°C)...............................727mW

8-Pin Plastic SO (derate 5.88mW/°C above +70°C) ....471mW

6-Pin TDFN-EP (derate 18.2mW above +70°C) .........1454mW

Operating Temperature Range .........................-40°C to +125°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

Soldering Temperature (reflow)

Lead(Pb)-Free Packages.............................................+260°C

Packages Containing Lead..........................................+240°C

Input Offset Voltage VOS (Note 1) 0.1 2 µV

Long-Term Offset Drift 50 nV/1000hr

Input Bias Current IB (Note 2) 1 pA

Input Offset Current IOS (Note 2) 2 pA

Peak-to-Peak Input Noise
Voltage

Input Voltage-Noise Density en f = 1kHz 30 NV/Hz

Common-Mode Input
Voltage Range

Common-Mode Rejection Ratio CMRR -0.1V  VCM VCC - 1.3V (Note 1) 120 140 dB

Power-Supply Rejection Ratio PSRR 2.7V  VCC 5.5V (Note 1) 120 140 dB

Large-Signal Voltage Gain A

Output Voltage Swing VOH/V

Output Short-Circuit Current To either suppl y 40 mA

Output Leakage Current 0  V

Slew Rate

Gain- Bandwidth Product GBWP

Min imum Stable Clo sed-Loop
Gain

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

e

RS = 100, 0.01Hz to 10Hz 1.5 µV

nP-P

Inferred from CMRR test

V

CM

VOL

OL

0.05V  V
(Note 1)

0.1V  V
(Note 1)

RL = 10k

RL = 1k

V
V

R
measured at f = 100kHz

RL = 10k, CL = 100pF,
phase margin = 60°

OUT

OUT

 VCC, SHDN = GND (Note 2) 0.01 1 µA

OUT

= 5V, CL = 100pF,

CC

= 2V step

OUT

= 10k, CL = 100pF,

L

V

CC

- 1.3

 VCC - 0.05V

 VCC - 0.1V

V

GND

- 0.1

= 10k 125 150

R

L

= 1k 125 145

R

L

VCC - VOH 4 10

4 10

V

OL

VCC - VOH 35 50

35 50

V

OL

MAX4238 0.35

MAX4239 1.6

MAX4238 1

MAX4239 6.5

MAX4238 1

MAX4239 10

P-P

V

dB

mV

V/µs

MHz

V/V

MAX4238/MAX4239

Ultra-Low Offset/Drift, Low-Noise,

Precision SOT23 Amplifiers

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(2.7V ≤ VCC≤ 5.5V, VCM= V

GND

= 0V, V

OUT

= VCC/2, RL= 10kΩ connected to VCC/2, SHDN = VCC, TA= +25°C,

unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Max imum Closed-Loop Gain

Settling Time -1V step

Overload Reco ver y Time

Startup Time AV = 10

Supply Voltage Range VCC Inferred by PSRR test 2.7 5.5 V

Supply Current I

Shutdown Logic-High VIH 2.2 V

Shutdown Logic-Low VIL 0.8 V

Shutdown Input Current 0V  V

CC

= 10k, CL = 100pF,

R

L

phase margin = 60°

A

= 10

V

(Note 4)

SHDN = VCC, no load, VCC = 5.5V 600 850
SHDN = GND, VCC = 5.5V 0.1 1

 VCC 0.1 1 µA

SHDN

MAX4238 1000

MAX4239 6700

0.1% (10 bit) 0.5

0.025% (12 bit) 1.0

0.006% (14 bit) 1.7

0.0015% (16 bit) 2.3

0.1% (10 bit) 3.3

0.025% (12 bit) 4.1

0.006% (14 bit) 4.9

0.0015% (16 bit) 5.7

0.1% (10 bit) 1.8

0.025% (12 bit) 2.6

0.006% (14 bit) 3.4

0.0015% (16 bit) 4.3

V/V

ms

ms

ms

µA

MAX4238/MAX4239

Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(2.7V ≤ VCC≤ 5.5V, VCM= GND = 0V, V

OUT

= VCC/2, RL= 10kΩ connected to VCC/2, SHDN = VCC, TA= -40°C to +125°C, unless other-

wise noted.) (Note 5)

Note 1: Guaranteed by design. Thermocouple and leakage effects preclude measurement of this parameter during production

testing. Devices are screened during production testing to eliminate defective units.

Note 2: IN+ and IN- are gates to CMOS transistors with typical input bias current of 1pA. CMOS leakage is so small that it is

impractical to test and guarantee in production. Devices are screened during production testing to eliminate defective units.

Note 3: Leakage does not include leakage through feedback resistors.
Note 4: Overload recovery time is the time required for the device to recover from saturation when the output has been

driven to either rail.

Note 5: Specifications are 100% tested at T

A

= +25°C, unless otherwise noted. Limits over temperature are guaranteed by design.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Input Offset Voltage VOS (Note 1)

Input Offset Drift TCVOS (Note 1) 10 nV/°C

Common-Mode Input Voltage
Range

Common-Mode Rejection Ratio CMRR

Power-Supply Rejection Ratio PSRR 2.7V  VCC 5.5V (Note 1) 120 dB

Large-Signal Voltage Gain A

Output Voltage Swing VOH/V

Output Leakage Current

Supply Voltage Range VCC Inferred by PSRR test 2.7 5.5 V

Supply Current I

Shutdown Logic High VIH 2.2 V

Shutdown Logic Low VIL 0.7 V

Shutdown Input Current 0V  V

TA = -40°C to +85°C 2.5

= -40°C to +125°C 3.5

T

A

V

V

Inferred from CMRR test

CM

- 0.05V 

V

GND

V

 VCC -

CM

1.4V (Note 1)

RL = 10k,

0.1V  V
 VCC - 0.1V
(Note 1)

VOL

RL = 1k
(Note 1)

RL = 10k

OL

RL = 1k

0V  V
(Note 3)

CC

SHDN = VCC, no load, VCC = 5.5V 900
SHDN = GND, VCC = 5.5V 2

OUT

OUT

SHDN

TA = -40°C to +85°C 115

= -40°C to +125°C 90

T

A

TA = -40°C to +85°C 125

= -40°C to +125°C 95

T

A

0.1V  V
T

= -40°C to +85°C

A

0.2V  V
= -40°C to +125°C

T

A

VCC - VOH 20

20

V

OL

VCC - VOH 100

100

V

OL

 VCC, SHDN = GND

 VCC 2 µA

 VCC - 0.1V,

OUT

 VCC - 0.2V,

OUT

GND

- 0.05

120

80

2 µA

V

CC

- 1.4

µV

V

dB

dB

dB

mV

µA

MAX4238/MAX4239

Ultra-Low Offset/Drift, Low-Noise,

Precision SOT23 Amplifiers

_______________________________________________________________________________________

5

Typical Operating Characteristics

(VCC= 5V, VCM= 0V, RL= 10kΩ connected to VCC/2, SHDN = VCC, TA= +25°C, unless otherwise noted.)

INPUT OFFSET DISTRIBUTION

50

40

30

20

PERCENTAGE OF UNITS (%)

10

0

OFFSET VOLTAGE (µV)

MAX4238/39 toc01

1.51.20.90.60.30-0.3-0.6-0.9-1.2-1.5

OUTPUT HIGH VOLTAGE

vs. OUTPUT SOURCE CURRENT

0.30

VOH = VCC - V

0.25

0.20

0.15

0.10

OUTPUT HIGH VOLTAGE (V)

0.05

0

020

OUT

MAX4238/39 toc04

VCC = 2.7V

VCC = 5V

15105

SOURCE CURRENT (mA)

OFFSET VOLTAGE vs. SUPPLY VOLTAGE

0.4

TA = +125°C

0.2

TA = +25°C

0

OFFSET VOLTAGE (µV)

-0.2

-0.4

2.7 5.5
SUPPLY VOLTAGE (V)

TA = -40°C

4.84.13.4

MAX4238/39 toc02

OFFSET VOLTAGE (µV)

OUTPUT LOW VOLTAGE

vs. OUTPUT SINK CURRENT

0.35

0.30

0.25

0.20

0.15

0.10

OUTPUT LOW VOLTAGE (V)

0.05

0

020

VCC = 2.7V

VCC = 5V

15105

SINK CURRENT (mA)

MAX4238/39 toc05

-100

-120

GAIN AND PHASE (dB/DEGREES)

-140

-160

-180

vs. COMMON-MODE VOLTAGE

0.4

TA = +125°C

0.2

0

-0.2

-0.4
0 3.6

COMMON-MODE VOLTAGE (V)

GAIN AND PHASE vs. FREQUENCY

80
60
40
20

0

-20

-40

-60

-80

VCC = 5V
GAIN = 60dB

Ω

= 10k

R

L

= 0pF

C

L

100 10M

OFFSET VOLTAGE

TA = +25°C

MAX4238

FREQUENCY (Hz)

MAX4238/39 toc03

TA = -40°C

2.71.80.9

MAX4238/39 toc06

1M100k10k1k

GAIN AND PHASE vs. FREQUENCY

MAX4238

80
60
40
20

0

-20

-40

-60

-80

-100
VCC = 5V

-120

GAIN AND PHASE (dB/DEGREES)

GAIN = 60dB

-140

= 10kΩ

R

L

-160

= 100pF

C

L

-180

100 10M

FREQUENCY (Hz)

MAX4238

GAIN AND PHASE vs. FREQUENCY

80
60

MAX4238/39 toc07

1M100k10k1k

40
20

0

-20

-40

-60

-80

-100
VCC = 5V

-120

GAIN AND PHASE (dB/DEGREES)

GAIN = 40dB

-140

= 10kΩ

R

L

-160

= 0pF

C

L

-180

100 10M

FREQUENCY (Hz)

MAX4238/39 toc08

1M100k10k1k

GAIN AND PHASE vs. FREQUENCY

80
60
40
20

0

-20

-40

-60

-80

-100
VCC = 5V

-120

GAIN AND PHASE (dB/DEGREES)

GAIN = 40dB

-140

= 10kΩ

R

L

-160

= 68pF

C

L

-180

100 10M

MAX4238

MAX4238/39 toc09

1M100k10k1k

FREQUENCY (Hz)

MAX4238/MAX4239

Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VCC= 5V, VCM= 0V, RL= 10kΩ connected to VCC/2, SHDN = VCC, TA= +25°C, unless otherwise noted.)

COMMON-MODE REJECTION RATIO

vs. FREQUENCY

MAX4238/39 toc14

FREQUENCY (kHz)

CMRR (dB)

100100.1 1

-140

-120

-100

-80

-60

-40

-20

0

0.01 1000

-160

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

MAX4238/39 toc13

FREQUENCY (kHz)

PSRR (dB)

100100.1 1

-140

-120

-100

-80

-60

-40

-20

0

-160

0.01 1000

MAX4239

GAIN AND PHASE vs. FREQUENCY

MAX4238/39 toc10

FREQUENCY (Hz)

GAIN AND PHASE (dB/DEGREES)

1E+61E+51E+41E+3

-160

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

80

-180
1E+2 1E+7

VCC = 5V
GAIN = 40dB
R

L

= 10k

Ω

C

L

= 0pF

MAX4239

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4238/39 toc17

AV = 10V/V
R

L

= 2kΩ

C

L

= 100pF

10µs/div

OUT

IN

500mV/div

50mV/div

MAX4238

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4238/39 toc15

AV = 1V/V
R

L

= 2kΩ

C

L

= 100pF

10µs/div

OUT

IN

1V/div

1V/div

MAX4239

GAIN AND PHASE vs. FREQUENCY

MAX4238/39 toc11

FREQUENCY (Hz)

GAIN AND PHASE (dB/DEGREES)

1E+61E+51E+41E+3

-160

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

80

-180
1E+2 1E+7

VCC = 5V
GAIN = 40dB
R

L

= 10kΩ

C

L

= 100pF

OVERVOLTAGE RECOVERY TIME

MAX4238/39 toc18

AV = 100V/V
R

L

= 10kΩ

V

CC

= 2.5V

V

EE

= -2.5V

400µs/div

0

0

OUT

IN

1V/div

50mV/div

MAX4238

SMALL-SIGNAL TRANSIENT RESPONSE

MAX4238/39 toc16

AV = 1V/V
R

L

= 2kΩ

C

L

= 100pF

10µs/div

OUT
50mV/div

IN
50mV/div

SUPPLY CURRENT vs. SUPPLY VOLTAGE

MAx4238/39 toc12

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

4321

200

300

400

500

600

0

100

05

TA = +125°C

TA = +25°C

TA = -40°C

Detailed Description

The MAX4238/MAX4239 are high-precision amplifiers
that have less than 2.5µV of input-referred offset and
low 1/f noise. These characteristics are achieved
through a patented autozeroing technique that samples
and cancels the input offset and noise of the amplifier.
The pseudorandom clock frequency varies from 10kHz
to 15kHz, reducing intermodulation distortion present in
chopper-stabilized amplifiers.

Offset Error Sources

To achieve very low offset, several sources of error
common to autozero-type amplifiers need to be consid­ered. The first contributor is the settling of the sampling
capacitor. This type of error is independent of input­source impedance, or the size of the external gain-set­ting resistors. Maxim uses a patented design technique
to avoid large changes in the voltage on the sampling
capacitor to reduce settling time errors.

The second error contributor, which is present in both
autozero and chopper-type amplifiers, is the charge
injection from the switches. The charge injection
appears as current spikes at the input, and combined
with the impedance seen at the amplifier’s input, con­tributes to input offset voltage. Minimize this
feedthrough by reducing the size of the gain-setting
resistors and the input-source impedance. A capacitor
in parallel with the feedback resistor reduces the
amount of clock feedthrough to the output by limiting
the closed-loop bandwidth of the device.

The design of the MAX4238/MAX4239 minimizes the
effects of settling and charge injection to allow specifi­cation of an input offset voltage of 0.1µV (typ) and less
than 2.5µV over temperature (-40°C to +85°C).

1/f Noise

1/f noise, inherent in all semiconductor devices, is
inversely proportional to frequency. 1/f noise increases
3dB/octave and dominates amplifier noise at lower fre­quencies. This noise appears as a constantly changing
voltage in series with any signal being measured. The
MAX4238/MAX4239 treat 1/f noise as a slow varying
offset error, inherently canceling the 1/f noise.

MAX4238/MAX4239

Ultra-Low Offset/Drift, Low-Noise,

Precision SOT23 Amplifiers

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(VCC= 5V, VCM= 0V, RL= 10kΩ connected to VCC/2, SHDN = VCC, TA= +25°C, unless otherwise noted.)

SHUTDOWN WAVEFORM

MAX4238/39 toc20

RL = 10kΩ
C

L

= 100pF

10µs/div

OUT

2V/div

1V/div

SHDN

DC TO 10Hz NOISE

MAX4238/39 toc19

VCC = 2.5V
V

EE

= -2.5V

1s/div

OUT

2µV/div

Pin Description

PIN

TDFN SOT23 SO

1 1 6 OUT Amp lifier Output

2 2 4 GND Ground

3 3 3 IN+ Noninverting Input

4 4 2 IN- Inverting Input

5 5 1 SHDN

6 6 7 VCC Positive Power Supply

— — 5, 8 N.C.

— — — EP

NAME FUNCTION

Shutdown Input. Active-low
shutdown, connect to V
for normal operation.

No Connection. Not
internally connected.

Exposed Pad (TDFN only).
Connect EP to GND.

CC

MAX4238/MAX4239

Output Overload Recovery

Autozeroing amplifiers typically require a substantial
amount of time to recover from an output overload. This
is due to the time it takes for the null amplifier to correct
the main amplifier to a valid output. The MAX4238/
MAX4239 require only 3.3ms to recover from an output
overload (see

Electrical Characteristics

and

Typical

Operating Characteristics

).

Shutdown

The MAX4238/MAX4239 feature a low-power (0.1µA)
shutdown mode. When SHDN is pulled low, the clock
stops and the device output enters a high-impedance
state. Connect SHDN to VCCfor normal operation.

Applications Information

Minimum and Maximum Gain

Configurations

The MAX4238 is a unity-gain stable amplifier with a gain­bandwidth product (GBWP) of 1MHz. The MAX4239 is
decompensated for a GBWP of 6.5MHz and is stable with
a gain of 10V/V. Unlike conventional operational ampli­fiers, the MAX4238/MAX4239 have a maximum gain
specification. To maintain stability, set the gain of the
MAX4238 between AV= 1000V/V to 1V/V, and set the
gain of the MAX4239 between AV= 6700V/V and 10V/V.

ADC Buffer Amplifier

The low offset, fast settling time, and 1/f noise cancella­tion of the MAX4238/MAX4239 make these devices
ideal for ADC buffers. The MAX4238/MAX4239 are well
suited for low-speed, high-accuracy applications such
as strain gauges (see

Typical Application Circuit

).

Error Budget Example

When using the MAX4238/MAX4239 as an ADC buffer,
the temperature drift should be taken into account when
determining the maximum input signal. With a typical off­set drift of 10nV/°C, the drift over a 10°C range is 100nV.
Setting this equal to 1/2LSB in a 16-bit system yields a
full-scale range of 13mV. With a single 2.7V supply, an
acceptable closed-loop gain is AV= 200. This provides
sufficient gain while maintaining headroom.

Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers

8 _______________________________________________________________________________________

Pin Configurations

Chip Information

PROCESS: BiCMOS

Package Information

For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages

. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE NO.

LAND

PATTERN NO.

6 SOT23 U6F-6

21-0058

90-0175

8 SO S8-4

21-0041

90-0096

6 TDFN T633+2

21-0137 90-0058

SHDN

IN-

IN+

TOP VIEW

1

2

3

4

+

(3mm x 3mm x 0.8mm)

*CONNECT EP TO GND.

MAX4238/

MAX4239

SO

CC

V

SHDN4IN-

6

5

EP*

MAX4238/

MAX4239

1

23

OUT

87N.C.

V

OUT

6

N.C.GND

5

TDFN

CC

IN+

GND

MAX4238/

MAX4239

16V

OUT

GND

2

34

SOT23

5 SHDN

CC

IN-IN+

MAX4238/MAX4239

Ultra-Low Offset/Drift, Low-Noise,

Precision SOT23 Amplifiers

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in
the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

9

_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

Revision History

REVISION
NUMBER

2 5/06 — —

3 8/11 Added MAX4238 and MAX4239 automotive-qualified parts 1

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