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MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
General Description
The MAX44284 is a high-side, current-sense amplifier
that operates with a 1.7V to 5.5V single supply and is
optimized for very low power operation with only 21µA of
quiescent current.
The MAX44284 offers precision accuracy specifications
of 2μV VOS and gain error of 0.05%. The device features
an input common-mode voltage range from -0.1V to
+36V. This current-sense amplifier has a voltage output
and is offered in four different gain versions.
Benefits and Features
● Supports Use of Small Current-Sense Resistors to
Improve Power-Supply Conversion Efficiency and
Measurement Accuracy
• Input Bias Current of 80nA (max)
• Very Low 2μV Input Offset Voltage (MAX44284F/H)
• Extremely Low 50nV/°C Input Offset Tempco
Coefficient
• -0.1V to +36V Wide Input Common-Mode Range
• Low 0.05% Gain Error
The MAX44284 is offered in small 6-bump, 0.4mm-pitch
WLP (1.3mm x 0.9mm) and 6-pin SOT23 packages and is
specified for operation over the -40°C to +125°C automotive
temperature range.
● Extends Battery Life
• Low Supply Current of 21μA
• 1.7V to 5.5V Single Supply
• Shutdown Input (Independent of VDD)
Applications
● Four Fixed Gain Options Simplify Design
• 50V/V – MAX44284F
• 100V/V – MAX44284H
• 200V/V – MAX44284W
• 500V/V – MAX44284E
●
●
●
●
●
●
Smartphones and Tablets
Notebook Computers
DC-DC Current Sensing in Power Management
Portable-/Battery-Powered Systems
Medical Pulse Oximeters and Infusion Pumps
Base Stations
Ordering Information appears at end of data sheet.
Typical Application Circuit
ILOAD
RSENSE
VBATT = UP TO 36V
RS+
RS-
LOAD
VDD = 3.3V
OUT
MAX44284
VDD = 3.3V
µC
ADC
19-6862; Rev 10; 6/20
© 2020 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners.
One Analog Way, Wilmington, MA 01887 U.S.A.
|
Tel: 781.329.4700
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© 2020 Analog Devices, Inc. All rights reserved.
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Absolute Maximum Ratings
VDD to GND.............................................................-0.3V to +6V
RS+, RS- to GND...................................................-0.3V to +40V
RS+ to RS-...........................................................................±40V
OUT, SHDN to GND.................................. -0.3V to (VDD + 0.3V)
Continuous Input Current (any pin)...................................±20mA
Continuous Power Dissipation (TA = +70°C)
WLP (derate 10.5mW/°C above +70°C).......................840mW
SOT23 (derate 4.3mW/°C above +70°C)..................347.8mW
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)........................................+260°C
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.
Package Information
6 SOT23
PACKAGE CODE
U6+1, U6+1A
Outline Number
21-0058
Land Pattern Number
90-0175
Thermal Resistance, Single-Layer Board:
Junction to Ambient - θJA (C/W)
N/A
Junction to Case - θJC (C/W)
80
Thermal Resistance, Multi-Layer Board
Junction to Ambient (θJA) (C/W)
115
Junction to Case (θJC) (C/W)
80
6 WLP
PACKAGE CODE
W60A1+1
Outline Number
21-0656
Land Pattern Number
Refer to Application Note 1891
Thermal Resistance, Multi-Layer Board
Junction to Ambient (θJA) (C/W)
95.15
Junction to Case (θJC) (C/W)
N/A
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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 thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board.
For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
www.analog.com
Analog Devices │ 2
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Electrical Characteristics
(VDD = 3.3V, VCM = 12V, VSENSE = VFS/2, VFS = (VDD - VOH - VOL)/Gain, VSHDN = VDD, RL = 10kΩ to GND, TA = -40°C to +125°C,
unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
0.3
0.8
μA
21
31.2
POWER SUPPLY
Supply Voltage
Shutdown Supply Current
Supply Current
VDD
Guaranteed by PSRR
1.7
ISHDN
IDD
Power-Supply Rejection
Ratio
PSRR
Shutdown Voltage Low
VIL
Shutdown Voltage High
VIH
TA = +25°C, RL= ∞
-40°C ≤ TA ≤ +125°C, RL= ∞
1.7V ≤ VDD ≤ 5.5V, VOUT = 1V
41.5
100
110
μA
dB
0.55
1.3
V
V
DC CHARACTERISTICS
Input Common-Mode Voltage
Range
Common-Mode Rejection
Ratio (Note 5)
Input Bias Current
Input Offset Current
VCM
CMRR
Guaranteed by CMRR
-0.1
+36
-0.1V ≤ VCM ≤ +36V, VCM = RS-
91.3
140
+0.1V ≤ VCM ≤ +36V, VCM = RS(Note 7)
120
145
2
80
nA
IOS
2
50
nA
±2
±10
MAX44284F
(-40°C ≤ TA ≤ +125°C)
MAX44284H (TA = +25°C)
VOS
±28
±2
MAX44284H
(-40°C ≤ TA ≤ +125°C)
MAX44284W (TA = +25°C)
MAX44284E (TA = +25°C)
±10
Gain
www.analog.com
G
±20.5
μV
±38
±15
MAX44284E
(-40°C ≤ TA ≤ +125°C)
TCVOS
±12
±28
MAX44284W
(-40°C ≤ TA ≤ +125°C)
Input Offset Voltage
Temperature Drift
dB
IRS+, IRSMAX44284F (TA = +25°C)
Input Offset Voltage (Note 3)
V
±26
±40
50
MAX44284F
50
MAX44284H
100
MAX44284W
200
MAX44284E
500
nV/°C
V/V
Analog Devices │ 3
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Electrical Characteristics (continued)
(VDD = 3.3V, VCM = 12V, VSENSE = VFS/2, VFS = (VDD - VOH - VOL)/Gain, VSHDN = VDD, RL = 10kΩ to GND, TA = -40°C to +125°C,
unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MAX44284F (TA = +25°C)
MIN
TYP
MAX
0.05
0.15
MAX44284F
(-40°C ≤TA ≤ +125°C)
MAX44284H (TA = +25°C)
Gain Error (Note 4)
GE
0.20
0.05
MAX44284H
(-40°C ≤ TA ≤ +125°C)
MAX44284W (TA = +25°C)
0.05
Output Voltage High
VOH
0.05
VOL
No load
25
Output Impedance
0.16
35
mV
20
0.3
ISINK = 100µA
Input Differential Impedance
%
0.39
ISOURCE = 100μA
Output Voltage Low
0.15
0.35
MAX44284E
(-40°C ≤ TA ≤ +125°C)
VOH = VDD - VOUT,
RL = 10kΩ to GND
0.15
0.26
MAX44284W
(-40°C ≤ TA ≤ +125°C)
MAX44284E (TA = +25°C)
UNITS
1
20
mV
6
MΩ
200
mΩ
AC CHARACTERISTICS
Small-Signal Bandwidth
Input Voltage-Noise Density
AC Common-Mode Rejection
Ratio
www.analog.com
BW3dB
en
AC CMRR
MAX44284F
3
MAX44284H
1.8
MAX44284W
1
MAX44284E
0.4
f = 1kHz
150
nV/√Hz
f = 10kHz, 600mVP-P sinusoidal
waveform
80
dB
kHz
Analog Devices │ 4
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Electrical Characteristics (continued)
(VDD = 3.3V, VCM = 12V, VSENSE = VFS/2, VFS = (VDD - VOH - VOL)/Gain, VSHDN = VDD, RL = 10kΩ to GND, TA = -40°C to +125°C,
unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
Settling Time
Capacitive Load
SYMBOL
tS
CL
CONDITIONS
MIN
TYP
VOUT from 250mV to 2.5V,
Gain = 50, within 12-bit accuracy
1500
VOUT from 250mV to 2.5V,
Gain = 100, within 12-bit
accuracy
1500
VOUT from 250mV to 2.5V,
Gain = 200, within 12-bit
accuracy
1800
VOUT from 250mV to 2.5V,
Gain = 500, within 12-bit
accuracy
4000
RISO = 0Ω
500
RISO = 20Ω
2200
MAX
UNITS
µs
pF
Note 2: All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design.
Note 3: VOS is calculated by applying two values of VSENSE (10% of full-scale range to 90% of full-scale range).
Note 4: Gain error is calculated by applying two values of VSENSE (10% of full-scale range to 90% of full-scale range) and calculating the error of the slope vs. the ideal.
Note 5: CMRR measurement is done at VOUT = VDD/2 condition.
Note 6: PSRR measurement is done at VOUT = 1V condition.
Note 7: Parameter is guaranteed by design.
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Analog Devices │ 5
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. TEMPERATURE
27
VDD = 3.3V
VDD = 5.5V
25
23
21
17
-50
-25
0
25
50
VDD = 3.3V
28
26
24
75
100
20
125
32
-50
0
25
50
75
TEMPERATURE (°C)
29
28
VDD = 3.3V
26
25
-25
0
25
50
75
100
16
HISTOGRAM
8
6
4
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
GAIN ERROR (%)
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100
125
TA = +125ºC
24
23
TA = +85ºC
-1
4
9
14
TA = +25ºC
19
24
29
34
INPUT OFFSET VOLTAGE HISTOGRAM
HISTOGRAM
20
15
10
0
16
GAIN = 50V/V
GAIN = 100V/V
14
toc04b
HISTOGRAM
GAIN = 200V/V
12
10
8
6
4
5
2
75
25
toc04a
25
OCCURRENCE N (%)
OCCURRENCE N (%)
30
ALL GAIN
OPTIONS
10
50
TA = -40ºC
26
INPUT OFFSET VOLTAGE HISTOGRAM
12
25
VCM (V)
toc03
14
0
27
OCCURRENCE N (%)
GAIN ERROR HISTOGRAM
0
28
20
125
TEMPERATURE (°C)
18
-25
VDD = 3.3V
21
-50
-50
22
VDD = 1.7V
23
VDD = 1.7V
SUPPLY CURRENT
vs. COMMON VOLTAGE
30
VDD = 5.5V
24
20
TEMPERATURE (°C)
29
27
VDD = 3.3V
21
17
125
toc01d
30
22
100
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
-25
GAIN = 500V/V
31
22
18
TEMPERATURE (°C)
SUPPLY CURRENT
vs. TEMPERATURE
VDD = 5.5V
23
19
VDD = 1.7V
22
toc01c
GAIN = 200V/V
24
VDD = 5.5V
30
VDD = 1.7V
19
SUPPLY CURRENT
vs. TEMPERATURE
25
GAIN = 100V/V
32
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
29
34
toc01b
MAX44284 toc02
GAIN = 50V/V
toc01a
SUPPLY CURRENT (µA)
SUPPLY CURRENT
vs. TEMPERATURE
2
0
-6
-4
-2
0
2
4
INPUT OFFSET VOLTAGE (μV )
6
-20-18-16-14-12-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20
INPUT OFFSET VOLTAGE ( μV )
Analog Devices │ 6
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
toc05
8
HISTOGRAM
6
5
4
3
2
VDD = 5.5V
0.5
0.4
VDD = 3.3V
0.3
VDD = 1.7V
0.2
1
0
GAIN = 50V/V
0.6
SUPPLY CURRENT (µA)
OCCURRENCE N (%)
0.7
ALL GAIN
OPTIONS
7
MAX44284 toc06
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
INPUT OFFSET VOLTAGE DRIFT HISTOGRAM
0.1
-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60
INPUT OFFSET VOLTAGE DRIFT (nV/°C)
0
-40 -20
0
20
40
60
80
100 120
TEMPERATURE (°C)
MAX44284 toc07
VDD = 3.3V
800
700
800
700
VOL (mV)
400
300
600
500
400
300
200
200
100
100
0
1
2
4
5
6
7
8
9
0
10
0
2
4
10
INPUT OFFSET VOLTAGE
vs. TEMPERATURE
GAIN ERROR
vs. INPUT COMMON-MODE VOLTAGE
25
toc09
0.05
0.04
20
GAIN = 200
10
8
ISINK (mA)
GAIN = 50V/V
15
6
IOUT (mA)
GAIN ERROR (%)
INPUT OFFSET VOLTAGE (µV)
30
3
MAX44284 toc10
VOH (mV)
500
GAIN = 50VV
GAIN =
100V/V
5
0
VDD = 3.3V
900
600
0
VOL vs. ISINK
1000
MAX44284 toc08
VOH vs. IOUT
900
0.03
0.02
0.01
-50
-25
0
25
50
75
TEMPERATURE (°C)
100
125
0
-0.1
4.9
9.9
14.9 19.9 24.9 29.9 34.9
VCM (V)
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Analog Devices │ 7
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
0.045
0.040
0.035
0.030
0.025
0.020
0.04
GAIN = 100V/V
0.02
-0.02
0.010
0.005
-0.04
1.7 2.1 2.5 2.8 3.2 3.6 4.0 4.4 4.7 5.1 5.5
VDD (V)
120
VCM = -0.1V to +36V
110
75
100
125
POWER-SUPPLY REJECTION RATIO
vs. TEMPERATURE
110
100
90
80
90
-50
-25
0
25
50
75
TEMPERATURE (ºC)
70
125
100
INPUT BIAS CURRENT
vs. INPUT COMMON-MODE VOLTAGE
toc15
200
12
TA = -40°C
10
0
TA =
+25°C
TA = +85°C
-200
INPUT BIAS CURRENT (nA)
INPUT BIAS CURRENT (nA)
50
120
100
-400
-600
-800
TA = +125°C
-1000
-1
3
7
11
15
19
23
27
31
-50
-25
0
25
50
75
TEMPERATURE (ºC)
INPUT BIAS CURRENT
vs. TEMPERATURE
VCM = 12V
100
125
toc16
FOR ALL GAIN
OPTIONS
8
6
4
2
0
-2
FOR ALL GAIN
OPTIONS
INPUT COMMON-MODE VOLTAGE(V)
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25
130
PSRR (dB)
CMRR (dB)
VCM = 0 to 36V
130
0
140
150
140
-25
MAX44284 toc14
160
-50
150
MAX44284 toc13
170
GAIN = 200 V/V
TEMPERATURE (°C)
COMMON-MODE REJECTION RATIO
vs. TEMPERATURE
180
-1200
GAIN = 500V/V
0
0.015
80
toc12
GAIN = 50V/V
0.06
GAIN ERROR (%)
GAIN ERROR (%)
0.08
MAX44284 toc11
0.050
0
GAIN ERROR
vs. TEMPERATURE
GAIN ERROR vs. SUPPLY VOLTAGE
35
-4
-40 -25 -10 5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
Analog Devices │ 8
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAGNITUDE (dB)
G = 200V/V
50
40
30
G = 100V/V
20
10
G = 50V/V
0
-10
-20
100
10
0
10
100
1k
10k
INPUT-VOLTAGE NOISE vs. FREQUENCY
MAX44284 toc18
G = 500V/V
60
1000
INPUT VOLTAGE NOISE (nV√Hz)
70
MAX44284 toc17
GAIN vs. FREQUENCY
80
100k
0.1
1
10
100
1k
10k
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
SMALL-SIGNAL INPUT STEP RESPONSE
(VDD = 3.3V, RL = Open, G = 100V/V)
0.1Hz TO 10Hz PEAK-TO-PEAK NOISE
MAX44284 toc20
MAX44284 toc19
6mV
VIN
3mV
VOUT
1µV/div
600mV
VOUT
300mV
1s/div
400µs/div
LARGE-SIGNAL INPUT STEP RESPONSE
(VCC = 3.3V, RL = Open)
MAX44284 toc21
3V
VOUT
0.3V
10000
ISOLATION RESISTOR (Ω)
3mV
STABLE
1000
100
10
UNSTABLE
1
0.1
0.01
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toc22
100000
30mV
VIN
400µs/div
STABILITY vs. CAPACITIVE
LOAD AND ISOLATION RESISTOR
100
1000
10000
100000
1000000
CAPACITIVE LOAD (pF)
Analog Devices │ 9
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Pin Configurations
TOP VIEW
TOP VIEW
VDD
1
+
6
SHDN
VDD
OUT
A1
A2
A3
B1
B2
B3
+
MAX44284
MAX44284
RS+
GND
2
5
OUT
RS+
3
4
RS-
RS-
SOT23
GND SHDN
WLP
Pin Description
PIN
BUMP
SOT23
WLP
1
A2
VDD
Power-Supply Voltage Input. Bypass VDD to GND with 0.1μF and 4.7μF
capacitors in parallel as close as possible to the device.
2
B2
GND
Ground
3
A1
RS+
External Sense Resistor Power-Side Connection
4
B1
RS-
External Sense Resistor Load-Side Connection
5
A3
OUT
Output Voltage. VOUT is proportional to VSENSE = VRS+ - VRS-.
6
B3
SHDN
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NAME
FUNCTION
Active-Low Shutdown Input. Connect to VDD for normal operation.
Analog Devices │ 10
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Detailed Description
The MAX44284 family features a single-supply; highaccuracy unidirectional, current-sense amplifier in various
gain options and a -0.1V to 36V input common-mode
range that is independent of supply voltage (VDD). The
MAX44284 is ideal for many battery-powered, handheld
devices because it uses only maximum 31.2μA quiescent
supply current to extend battery life. The device’s low
input offset voltage, tight gain error, and low temperature
drift characteristics allow the use of small-sense resistors
for current measurements to improve power-supply conversion efficiency and accuracy of measurements. This
feature allows monitoring of power-supply load current
even if the rail is shorted to ground. High-side current
monitoring does not interfere with the ground path of the
load being measured, making the IC particularly useful in
a wide range of high-reliability systems.
Because of its extended common-mode range below
ground, this part can also be used as a low-side current
sensing element.
Shutdown
The MAX44284 features active-low logic shutdown input
to reduce the supply current. Drive SHDN high for normal
operation. Drive SHDN low to place the device in shutdown mode. In shutdown mode, the supply current drawn
from the VDD is less than 1μA (max).
power dissipation in battery-powered systems, as well as
load regulation issues in low-voltage DC power supplies.
Working with error tolerances with very few internal
blocks in this architecture is instrumental in achieving a
gain error of less than 0.20% over the entire temperature
range of -40°C to +125°C.
Applications Information
Input Differential Signal Range
The MAX44284’s input structure is optimized for sensing small differential signals as low as 3.4mV full scale
(VFS) for high efficiency with lowest power dissipation in
the sense resistor, or 110mV full scale for high dynamic
range. The input differential signal range is determined
by the following equation for the MAX44248 family.
V(SENSE RANGE) =
The input differential voltage range is estimated for
VDD from 1.7V to 5.5V for different gain values of the
MAX44284 as shown in Table 1.
Ideally, the maximum load current develops the full-scale
sense voltage across the current-sense resistor. Choose
the gain needed to yield the maximum output voltage
required for the application:
V=
OUT GAIN × VSENSE
Precision
The MAX44284 uses capacitive-coupled Instrumentation
amplifier architecture that enables the part to achieve
over the top common-mode voltage ranges, high power
efficiency, high gain accuracy, and low-power design.
Low Offset Voltage and Low Gain Error
The MAX44284 utilizes Capacitive-Coupled Chopper
Instrumentation Amplifier (CCIA) architecture to achieve
a low-input offset voltage of less than 10µA. These techniques also enable extremely low-input offset voltage drift
over time and temperature to 50nV/°C. The precision VOS
specification allows accurate current measurements with
lower values of current-sense resistors, thus reducing
VDD
GAIN
Choosing the Sense Resistor
Voltage Loss
A high RSENSE value causes the power-source voltage
to drop due to IR loss. For minimal voltage loss, use the
lowest RSENSE value.
Accuracy
Use the below linear equation to calculate total error:
VOUT=
(GAIN ± GE) ×
VSENSE ± (GAIN × VOS )
Table 1. VSENSE Input Range
PART
GAIN (V/V)
VSENSE RANGE (mV) with VDD (1.7V)
VSENSE RANGE (mV) with VDD (5.5V)
MAX44284F
50
34
110
MAX44284H
100
17
55
MAX44284W
200
8.5
27.5
MAX44284E
500
3.4
11
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Analog Devices │ 11
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
A high RSENSE value allows lower currents to be measured more accurately because offsets are less significant
when the sense voltage is larger. Note that the tolerance and temperature coefficient of the chosen resistors
directly affect the precision of any measurement system. For best performance, select RSENSE to provide
approximately maximum input differential sense voltage of
110mV (MAX44284F) or 55mV (MAX44284H) or 27.5mV
(MAX44284W) or 11mV (MAX44284E) of sense voltage for
the full-scale current in each application. Sense resistors of
5mΩ to 100mΩ are available with 1% accuracy or better.
RSENSE
RIN
CIN
CIN
RS+
RS-
MAX44284
Efficiency and Power Dissipation
At high current levels, the I2R losses in RSENSE can be
significant. This should be taken into consideration when
choosing the resistor value and its power dissipation
(wattage) rating. The sense resistor’s value will drift if it
is allowed to heat up excessively. The precision VOS of
the MAX44284 allows the use of small sense resistors to
reduce power dissipation and reduce hot spots.
LOAD
RIN
OUT
GND
Figure 1. Differential Input Filtering
RSENSE
Kelvin Connections
Because of the high currents that may flow through
RSENSE based on the application, take care to eliminate
solder and parasitic trace resistance from causing errors
in the sense voltage. Either use a four-terminal currentsense resistor or use Kelvin (force and sense) PCB layout
techniques.
Input Filtering
Some applications of current-sense amplifiers need to
measure currents accurately even in the presence of both
differential and common-mode ripple, as well as a wide
variety of input transient conditions.
The MAX44284 allows two methods of filtering to help
improve performance in the presence of input commonmode voltage and input differential voltage transients.
Figure 1 shows a differential input filter. The capacitor
CIN across RS+ and RS- along with the resistor RIN helps
filter against input differential voltages and prevents them
from reaching the MAX44284. The corner frequency of
this filter is determined by the choice of RIN, CIN. Figure 2
shows a common-mode input filter. The choice of capacitance depends on corner frequency after RIN is chosen.
In case of mismatch or error in application design, an
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LOAD
RIN
RIN
CIN
RS+
RS-
MAX44284
OUT
GND
Figure 2. Input Common-Mode Filtering
additional DC error is accumulated as offset voltage and
increased gain error.
VOS =(R IN × I OFFSET ) + (DR IN × IBIAS )
DRIN is the resistance mismatch in RIN at RS+ and RS-.
If DRIN is too small, its effect can be neglected. Since
IOFFSET of the MAX44284 is smaller than 2nA, and if we
want to make sure VOS is lesser than 1µV range, choosing
R IN < (VOS ÷ I OFFSET )
Analog Devices │ 12
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
For gain error, it depends on its input impedance and RIN.
GainError = 2 ×
Note that load capacitance greater than approximately
2nF may cause instability unless a series resistor is present to help isolate the capacitor from the amplifier output.
Output stability with different values of load capacitor
and isolation resistor is shown in TOC22 of the Typical
Operating Characteristics.
−R IN
Z IN
Avoid additional gain error shift due to the effect of RIN.
For gain error, the MAX44284 is 0.15%. If the margin of
additional effect of RIN results in a gain error shift of less
than 0.02%, then:
R IN < Z IN × (
Bidirectional Application
Battery-powered systems may require a precise bidirectional
current-sense amplifier to accurately monitor the battery’s
charge and discharge currents. Measurements of the two
separate outputs with respect to GND yield an accurate
measure of the charge and discharge currents, respectively
(Figure 4).
0.02%
) = 600Ω
2
So RIN can be chosen ≤ 500Ω.
Output Filtering
The internal architecture of the MAX44284 suppresses the DC
offset, 1/f noise, and accumulates at higher frequencies so that
they can be filtered out. Hence, minute AC disturbances
can be observed at 10kHz and 20kHz. It is recommended
to add an output filter after the MAX44284 to avoid noise
and unwanted frequency disturbances at the output with
4kHz -3dB fc (see Figure 3).
(Suggested values of C and R: 22nF and 1.8kΩ, respectively.)
LOAD
CIN
MAX44284
RIN
RSENSE
RIN
RSCIN2
RS+
R
OUT
C
CIN
VBATT
Figure 3. Filtering
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Analog Devices │ 13
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
ILOAD
RSENSE
TO WALL-CUBE
CHARGER
VBATT
UP TO 36V
LOAD
RS+
RS-
RS+
RS-
VDD = 3.3V
OUT
MAX44284
OUT
MAX44284
µC
ADC
ADC
Figure 4. Bidirectional Application
Ordering Information
PART
GAIN (V/V)
TEMP RANGE
PIN-PACKAGE
TOP MARK
MAX44284FAWT+
50
-40°C to +125°C
6 WLP
+CX
MAX44284FAUT+
50
-40°C to +125°C
6 SOT23
+ACSF
MAX44284FAUT/V+T*
50
-40°C to +125°C
6 SOT23
—
MAX44284HAWT+
100
-40°C to +125°C
6 WLP
+CY
MAX44284HAUT+
100
-40°C to +125°C
6 SOT23
+ACSG
MAX44284WAWT+
200
-40°C to +125°C
6 WLP
+CZ
MAX44284WAUT+
200
-40°C to +125°C
6 SOT23
+ACSH
MAX44284EAWT+
500
-40°C to +125°C
6 WLP
+DA
MAX44284EAUT+
500
-40°C to +125°C
6 SOT23
+ACSI
+Denotes a lead(Pb)-free/RoHS-compliant package
*Future product—contact factory for availability.
Chip Information
PROCESS: BiCMOS
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Analog Devices │ 14
MAX44284
36V, Input Common-Mode, High-Precision,
Low-Power Current-Sense Amplifier
Revision History
REVISION
NUMBER
REVISION
DATE
0
12/13
Initial release
1
5/14
Updated Typical Operating Characteristics and the Ordering Information
8, 13
2
6/14
Corrected General Description and updated Electrical Characteristics globals
1–4
3
9/14
Released MAX44284E and updated the Electrical Characteristics
3, 13
4
1/15
Revised Benefits and Features section
1
5
11/17
Corrected typo in Output Filtering section
12
6
6/18
Updated TOC22
8
7
7/18
Updated Ordering Information table
13
8
8/18
Updated Package Information section and Typical Operating Characteristics
2, 8
9
5/19
Updated Typical Operating Characteristics and Output Filtering section
9, 13
10
6/20
Updated Electrical Characteristics table and Input Filtering section
3, 13
DESCRIPTION
PAGES
CHANGED
—
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is
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may result from its use.Specifications subject to change without notice. No license is granted by implicationor
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property of their respective owners.
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