IP+
IP+
IP–
IP–
IP
5
GND
2
4
1
3
ACS712
7
8
+5 V
VIOUT
VOUT
6
FILTER
VCC
CBYP
0.1 µF
CF
1 nF
Application 1. The ACS712 outputs an analog signal, VOUT .
that varies linearly with the uni- or bi-directional AC or DC
primary sampled current, IP , within the range specified. CF
is recommended for noise management, with values that
depend on the application.
ACS712
Description
The Allegro® ACS712 provides economical and precise
solutions for AC or DC current sensing in industrial, commercial,
and communications systems. The device package allows for
easy implementation by the customer. Typical applications
include motor control, load detection and management, switch-
mode power supplies, and overcurrent fault protection. The
device is not intended for automotive applications.
The device consists of a precise, low-offset, linear Hall circuit
with a copper conduction path located near the surface of the
die. Applied current flowing through this copper conduction
path generates a magnetic field which the Hall IC converts into a
proportional voltage. Device accuracy is optimized through the
close proximity of the magnetic signal to the Hall transducer.
A precise, proportional voltage is provided by the low-offset,
chopper-stabilized BiCMOS Hall IC, which is programmed
for accuracy after packaging.
The output of the device has a positive slope (>VIOUT(Q))
when an increasing current flows through the primary copper
conduction path (from pins 1 and 2, to pins 3 and 4), which is
the path used for current sampling. The internal resistance of
this conductive path is 1.2 mΩ typical, providing low power
loss. The thickness of the copper conductor allows survival of
ACS712-DS, Rev. 14
Features and Benefits
▪ Low-noise analog signal path
▪ Device bandwidth is set via the new FILTER pin
▪ 5 μs output rise time in response to step input current
▪ 80 kHz bandwidth
▪ Total output error 1.5% at TA = 25°C
▪ Small footprint, low-profile SOIC8 package
▪ 1.2 mΩ internal conductor resistance
▪ 2.1 kVRMS minimum isolation voltage from pins 1-4 to pins 5-8
▪ 5.0 V, single supply operation
▪ 66 to 185 mV/A output sensitivity
▪ Output voltage proportional to AC or DC currents
▪ Factory-trimmed for accuracy
▪ Extremely stable output offset voltage
▪ Nearly zero magnetic hysteresis
▪ Ratiometric output from supply voltage
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
Continued on the next page…
Approximate Scale 1:1
Package: 8 Lead SOIC (suffix LC)
Typical Application
TÜV America
Certificate Number:
U8V 06 05 54214 010
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
2
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Absolute Maximum Ratings
Characteristic Symbol Notes Rating Units
Supply Voltage VCC 8V
Reverse Supply Voltage VRCC –0.1 V
Output Voltage VIOUT 8V
Reverse Output Voltage VRIOUT –0.1 V
Reinforced Isolation Voltage VISO
Pins 1-4 and 5-8; 60 Hz, 1 minute, TA=25°C 2100 VAC
Maximum working voltage according to
UL60950-1 184 Vpeak
Basic Isolation Voltage VISO(bsc)
Pins 1-4 and 5-8; 60 Hz, 1 minute, TA=25°C 1500 VAC
Maximum working voltage according to
UL60950-1 354 Vpeak
Output Current Source IIOUT(Source) 3mA
Output Current Sink IIOUT(Sink) 10 mA
Overcurrent Transient Tolerance IP1 pulse, 100 ms 100 A
Nominal Operating Ambient Temperature TARange E –40 to 85 ºC
Maximum Junction Temperature TJ(max) 165 ºC
Storage Temperature Tstg –65 to 170 ºC
Selection Guide
Part Number Packing* TA
(°C)
Optimized Range, IP
(A)
Sensitivity, Sens
(Typ) (mV/A)
ACS712ELCTR-05B-T Tape and reel, 3000 pieces/reel –40 to 85 ±5 185
ACS712ELCTR-20A-T Tape and reel, 3000 pieces/reel –40 to 85 ±20 100
ACS712ELCTR-30A-T Tape and reel, 3000 pieces/reel –40 to 85 ±30 66
*Contact Allegro for additional packing options.
the device at up to 5× overcurrent conditions. The terminals of the
conductive path are electrically isolated from the signal leads (pins
5 through 8). This allows the ACS712 to be used in applications
requiring electrical isolation without the use of opto-isolators or
other costly isolation techniques.
The ACS712 is provided in a small, surface mount SOIC8 package.
The leadframe is plated with 100% matte tin, which is compatible
with standard lead (Pb) free printed circuit board assembly processes.
Internally, the device is Pb-free, except for flip-chip high-temperature
Pb-based solder balls, currently exempt from RoHS. The device is
fully calibrated prior to shipment from the factory.
Description (continued)
Parameter Specification
Fire and Electric Shock
CAN/CSA-C22.2 No. 60950-1-03
UL 60950-1:2003
EN 60950-1:2001
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
3
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
VCC
(Pin 8)
(Pin 7)
VIOUT
R
F(INT)
GND
(Pin 5)
FILTER
(Pin 6)
Dynamic Offset
Cancellation
IP+
(Pin 1)
IP+
(Pin 2)
IP−
(Pin 3)
IP−
(Pin 4)
Sense
Trim
Signal
Recovery
Sense Temperature
Coefficient Trim
0 Ampere
Offset Adjust
Hall Current
Drive
+5 V
IP+
IP+
IP–
IP–
VCC
VIOUT
FILTER
GND
1
2
3
4
8
7
6
5
Terminal List Table
Number Name Description
1 and 2 IP+ Terminals for current being sampled; fused internally
3 and 4 IP– Terminals for current being sampled; fused internally
5 GND Signal ground terminal
6 FILTER Terminal for external capacitor that sets bandwidth
7 VIOUT Analog output signal
8 VCC Device power supply terminal
Functional Block Diagram
Pin-out Diagram
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
4
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
COMMON OPERATING CHARACTERISTICS1 over full range of TA , CF = 1 nF, and VCC = 5 V, unless otherwise specified
Characteristic Symbol Test Conditions Min. Typ. Max. Units
ELECTRICAL CHARACTERISTICS
Supply Voltage VCC 4.5 5.0 5.5 V
Supply Current ICC VCC = 5.0 V, output open – 10 13 mA
Output Capacitance Load CLOAD VIOUT to GND – – 10 nF
Output Resistive Load RLOAD VIOUT to GND 4.7 – – k
Primary Conductor Resistance RPRIMARY TA = 25°C – 1.2 – m
Rise Time trIP = IP(max), TA = 25°C, COUT = open – 5 – s
Frequency Bandwidth f –3 dB, TA = 25°C; IP is 10 A peak-to-peak – 80 – kHz
Nonlinearity ELIN Over full range of IP– 1.5 – %
Symmetry ESYM Over full range of IP98 100 102 %
Zero Current Output Voltage VIOUT(Q) Bidirectional; IP = 0 A, TA = 25°C – VCC ×
0.5 –V
Power-On Time tPO Output reaches 90% of steady-state level, TJ = 25°C, 20 A present
on leadframe –35–s
Magnetic Coupling2– 12 – G/A
Internal Filter Resistance3RF(INT) 1.7 k
1Device may be operated at higher primary current levels, IP, and ambient, TA , and internal leadframe temperatures, TA , provided that the Maximum
Junction Temperature, TJ(max), is not exceeded.
21G = 0.1 mT.
3RF(INT) forms an RC circuit via the FILTER pin.
COMMON THERMAL CHARACTERISTICS1
Min. Typ. Max. Units
Operating Internal Leadframe Temperature TAE range –40 – 85 °C
Value Units
Junction-to-Lead Thermal Resistance2RJL Mounted on the Allegro ASEK 712 evaluation board 5 °C/W
Junction-to-Ambient Thermal Resistance RJA Mounted on the Allegro 85-0322 evaluation board, includes the power con-
sumed by the board 23 °C/W
1Additional thermal information is available on the Allegro website.
2The Allegro evaluation board has 1500 mm2 of 2 oz. copper on each side, connected to pins 1 and 2, and to pins 3 and 4, with thermal vias connect-
ing the layers. Performance values include the power consumed by the PCB. Further details on the board are available from the Frequently Asked
Questions document on our website. Further information about board design and thermal performance also can be found in the Applications Informa-
tion section of this datasheet.
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
5
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
x05B PERFORMANCE CHARACTERISTICS1 TA = –40°C to 85°C, CF = 1 nF, and VCC = 5 V, unless otherwise specified
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Optimized Accuracy Range IP–5 – 5 A
Sensitivity Sens Over full range of IP, TA = 25°C 180 185 190 mV/A
Noise VNOISE(PP) Peak-to-peak, TA = 25°C, 185 mV/A programmed Sensitivity,
CF = 47 nF, COUT = open, 2 kHz bandwidth –21– mV
Zero Current Output Slope IOUT(Q)
TA = –40°C to 25°C – –0.26 – mV/°C
TA = 25°C to 150°C – –0.08 – mV/°C
Sensitivity Slope Sens TA = –40°C to 25°C – 0.054 – mV/A/°C
TA = 25°C to 150°C – –0.008 – mV/A/°C
Total Output Error2ETOT IP =±5 A, TA = 25°C – ±1.5 – %
1Device may be operated at higher primary current levels, IP, and ambient temperatures, TA, provided that the Maximum Junction Temperature, TJ(max),
is not exceeded.
2Percentage of IP, with IP = 5 A. Output filtered.
x20A PERFORMANCE CHARACTERISTICS1 TA = –40°C to 85°C, CF = 1 nF, and VCC = 5 V, unless otherwise specified
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Optimized Accuracy Range IP–20 – 20 A
Sensitivity Sens Over full range of IP, TA = 25°C 96 100 104 mV/A
Noise VNOISE(PP) Peak-to-peak, TA = 25°C, 100 mV/A programmed Sensitivity,
CF = 47 nF, COUT = open, 2 kHz bandwidth –11– mV
Zero Current Output Slope IOUT(Q)
TA = –40°C to 25°C – –0.34 – mV/°C
TA = 25°C to 150°C – –0.07 – mV/°C
Sensitivity Slope Sens TA = –40°C to 25°C – 0.017 – mV/A/°C
TA = 25°C to 150°C – –0.004 – mV/A/°C
Total Output Error2ETOT IP =±20 A, TA = 25°C – ±1.5 – %
1Device may be operated at higher primary current levels, IP, and ambient temperatures, TA, provided that the Maximum Junction Temperature,
TJ(max), is not exceeded.
2Percentage of IP, with IP = 20 A. Output filtered.
x30A PERFORMANCE CHARACTERISTICS1 TA = –40°C to 85°C, CF = 1 nF, and VCC = 5 V, unless otherwise specified
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Optimized Accuracy Range IP–30 – 30 A
Sensitivity Sens Over full range of IP
, TA = 25°C 63 66 69 mV/A
Noise VNOISE(PP) Peak-to-peak, TA = 25°C, 66 mV/A programmed Sensitivity,
CF = 47 nF, COUT = open, 2 kHz bandwidth –7– mV
Zero Current Output Slope IOUT(Q)
TA = –40°C to 25°C – –0.35 – mV/°C
TA = 25°C to 150°C – –0.08 – mV/°C
Sensitivity Slope Sens TA = –40°C to 25°C – 0.007 – mV/A/°C
TA = 25°C to 150°C – –0.002 – mV/A/°C
Total Output Error2ETOT IP = ±30 A
, TA = 25°C – ±1.5 – %
1Device may be operated at higher primary current levels, IP, and ambient temperatures, TA, provided that the Maximum Junction Temperature,
TJ(max), is not exceeded.
2Percentage of IP, with IP = 30 A. Output filtered.
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
6
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
–40
25
85
150
TA (°C)
–40
25
85
150
TA (°C)
IP = 0 A IP = 0 A
VCC = 5 V VCC = 5 V
VCC = 5 V
VCC = 5 V; IP = 0 A,
After excursion to 20 A
Mean Supply Current versus Ambient Temperature
Sensitivity versus Sensed Current
200.00
190.00
180.00
170.00
160.00
150.00
140.00
130.00
120.00
110.00
100.00
Sens (mV/A)
186.5
186.0
185.5
185.0
184.5
184.0
183.5
183.0
182.5
182.0
181.5
181.0
Sens (mV/A)
Ip (A)
-6-4-20246
T
A
(°C)
T
A
(°C) T
A
(°C)
Mean I
CC
(mA)
10.30
10.25
10.20
10.15
10.10
10.05
10.00
9.95
9.90
9.85
9.80
9.75
-50 -25 0 25 50 75 125100 150
I
OM
(mA)
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
–4.5
–5.0
-50 -25 0 25 50 75 125100 150
Supply Current versus Supply Voltage
10.9
10.8
10.7
10.6
10.5
10.4
10.3
10.2
10.1
10.0
4.5 4.6 4.8
4.7 4.9 5.0 5.35.1 5.2 5.4 5.5
V
CC
(V)
I
CC
(mA)
T
A
(°C)
V
IOUT(Q)
(mV)
2520
2515
2510
2505
2500
2495
2490
2485
-50 -25 0 25 50 75 125100 150
T
A
(°C)
I
OUT(Q)
(A)
0.20
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
-50 -25 0 25 50 75 125100 150
Nonlinearity versus Ambient Temperature
0.6
0.5
0.4
0.3
0.2
0.1
0
–50 0–25 25 50 12575 100 150
E
LIN
(%)
T
A
(°C)
Mean Total Output Error versus Ambient Temperature
8
6
4
2
0
–2
–4
–6
–8
–50 0–25 25 50 12575 100 150
E
TOT
(%)
T
A
(°C)
Sensitivity versus Ambient Temperature
–50 0–25 25 50 12575 100 150
I
P
(A)
Output Voltage versus Sensed Current
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–7 –6 –5 –4 –3 –2 –1 0 1 234567
V
IOUT
(V)
Magnetic Offset versus Ambient Temperature
VCC = 5 V
0 A Output Voltage versus Ambient Temperature 0 A Output Voltage Current versus Ambient Temperature
Characteristic Performance
IP = 5 A, unless otherwise specified
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
7
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
–40
25
85
150
TA (°C)
–40
25
–20
85
125
TA (°C)
IP = 0 A IP = 0 A
VCC = 5 V
VCC = 5 V
VCC = 5 V
VCC = 5 V; IP = 0 A,
After excursion to 20 A
Mean Supply Current versus Ambient Temperature
Sensitivity versus Sensed Current
110.00
108.00
106.00
104.00
102.00
100.00
98.00
96.00
94.00
92.00
90.00
Sens (mV/A)
Ip (A)
TA (°C)
TA (°C)
Mean I
CC
(mA)
9.7
9.6
9.5
9.4
9.3
9.2
9.1
-50 -25 0 25 50 75 125100 150
Supply Current versus Supply Voltage
10.4
10.2
10.0
9.8
9.6
9.4
9.2
9.0
V
CC
(V)
I
CC
(mA)
Nonlinearity versus Ambient Temperature
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
–50 0–25 25 50 12575 100 150
E
LIN
(%)
TA (°C)
Mean Total Output Error versus Ambient Temperature
8
6
4
2
0
–2
–4
–6
–8
–50 0–25 25 50 12575 100 150
E
TOT
(%)
IP (A)
Output Voltage versus Sensed Current
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–25 –20 –15 –10 –5 0 5 10152025
V
IOUT
(V)
4.5 4.6 4.8
4.7 4.9 5.0 5.35.15.2 5.45.5
–25 –20 –15 –10 –5 051015
20 25
100.8
100.6
100.4
100.2
100.0
99.8
99.6
99.4
99.2
99.0
Sens (mV/A)
TA (°C)
Sensitivity versus Ambient Temperature
–50 0–25 25 50 12575 100 150
TA (°C)
I
OM
(mA)
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
–4.5
–5.0
-50 -25 0 25 50 75 125100 150
Magnetic Offset versus Ambient Temperature
0 A Output Voltage versus Ambient Temperature
TA (°C)
V
IOUT(Q)
(mV)
2525
2520
2515
2510
2505
2500
2495
2490
2485
-50 -25 0 25 50 75 125100 150
0 A Output Voltage Current versus Ambient Temperature
TA (°C)
I
OUT(Q)
(A)
0.25
0.20
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
-50 -25 0 25 50 75 125100 150
Characteristic Performance
IP = 20 A, unless otherwise specified
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
8
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Characteristic Performance
IP = 30 A, unless otherwise specified
–40
25
85
150
TA (°C)
–40
25
–20
85
125
TA (°C)
IP = 0 A IP = 0 A
VCC = 5 V
VCC = 5 V
VCC = 5 V
VCC = 5 V; IP = 0 A,
After excursion to 20 A
VCC = 5 V
Mean Supply Current versus Ambient Temperature
Sensitivity versus Sensed Current
70.00
69.00
68.00
67.00
66.00
65.00
64.00
63.00
62.00
61.00
60.00
Sens (mV/A)
Ip (A)
T
A
(°C)
T
A
(°C)
Mean I
CC
(mA)
9.6
9.5
9.4
9.3
9.2
9.1
9.0
8.9
-50 -25 0 25 50 75 125100 150
Supply Current versus Supply Voltage
10.2
10.0
9.8
9.6
9.4
9.2
9.0
V
CC
(V)
I
CC
(mA)
Nonlinearity versus Ambient Temperature
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
–50 0–25 25 50 12575 100 150
E
LIN
(%)
T
A
(°C)
Mean Total Output Error versus Ambient Temperature
8
6
4
2
0
–2
–4
–6
–8
–50 0–25 25 50 12575 100 150
E
TOT
(%)
I
P
(A)
Output Voltage versus Sensed Current
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–30 –20 –10 0 10 20 30
V
IOUT
(V)
4.5 4.6 4.8
4.7 4.9 5.0 5.35.1 5.2 5.4 5.5
–30 –20 –10 0 10 20 30
66.6
66.5
66.4
66.3
66.2
66.1
66.0
65.9
65.8
65.7
Sens (mV/A)
T
A
(°C)
Sensitivity versus Ambient Temperature
–50 0–25 25 50 12575 100 150
T
A
(°C)
I
OM
(mA)
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
–4.5
–5.0
-50 -25 0 25 50 75 125100 150
Magnetic Offset versus Ambient Temperature
T
A
(°C)
V
IOUT(Q)
(mV)
2535
2530
2525
2520
2515
2510
2505
2500
2495
2490
2485
-50 -25 0 25 50 75 125100 150
T
A
(°C)
I
OUT(Q)
(A)
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
-50 -25 0 25 50 75 125100 150
0 A Output Voltage versus Ambient Temperature 0 A Output Voltage Current versus Ambient Temperature
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
9
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Sensitivity (Sens). The change in device output in response to a
1 A change through the primary conductor. The sensitivity is the
product of the magnetic circuit sensitivity (G / A) and the linear
IC amplifier gain (mV/G). The linear IC amplifier gain is pro-
grammed at the factory to optimize the sensitivity (mV/A) for the
full-scale current of the device.
Noise (VNOISE). The product of the linear IC amplifier gain
(mV/G) and the noise floor for the Allegro Hall effect linear IC
(≈1 G). The noise floor is derived from the thermal and shot
noise observed in Hall elements. Dividing the noise (mV) by the
sensitivity (mV/A) provides the smallest current that the device is
able to resolve.
Linearity (ELIN). The degree to which the voltage output from
the IC varies in direct proportion to the primary current through
its full-scale amplitude. Nonlinearity in the output can be attrib-
uted to the saturation of the flux concentrator approaching the
full-scale current. The following equation is used to derive the
linearity:
where VIOUT_full-scale amperes = the output voltage (V) when the
sampled current approximates full-scale ±IP .
Symmetry (ESYM). The degree to which the absolute voltage
output from the IC varies in proportion to either a positive or
negative full-scale primary current. The following formula is
used to derive symmetry:
Quiescent output voltage (VIOUT(Q)). The output of the device
when the primary current is zero. For a unipolar supply voltage,
it nominally remains at VCC ⁄ 2. Thus, VCC = 5 V translates into
VIOUT(Q) = 2.5 V. Variation in VIOUT(Q) can be attributed to the
resolution of the Allegro linear IC quiescent voltage trim and
thermal drift.
Electrical offset voltage (VOE). The deviation of the device out-
put from its ideal quiescent value of VCC / 2 due to nonmagnetic
causes. To convert this voltage to amperes, divide by the device
sensitivity, Sens.
Accuracy (ETOT). The accuracy represents the maximum devia-
tion of the actual output from its ideal value. This is also known
as the total output error. The accuracy is illustrated graphically in
the output voltage versus current chart at right.
Accuracy is divided into four areas:
0 A at 25°C. Accuracy at the zero current flow at 25°C, with-
out the effects of temperature.
0 A over Δ temperature. Accuracy at the zero current flow
including temperature effects.
Full-scale current at 25°C. Accuracy at the the full-scale current
at 25°C, without the effects of temperature.
Full-scale current over Δ temperature. Accuracy at the full-
scale current flow including temperature effects.
Ratiometry. The ratiometric feature means that its 0 A output,
VIOUT(Q), (nominally equal to VCC/2) and sensitivity, Sens, are
proportional to its supply voltage, VCC
. The following formula is
used to derive the ratiometric change in 0 A output voltage,
VIOUT(Q)RAT (%).
The ratiometric change in sensitivity, SensRAT (%), is defined as:
Definitions of Accuracy Characteristics
100 1–
[{
[{
VIOUT_full-scale amperes – VIOUT(Q)
Δ gain × % sat ( )
2 (VIOUT_half-scale amperes – VIOUT(Q) )
100
VIOUT_+ full-scale amperes – VIOUT(Q)
VIOUT(Q) – VIOUT_–full-scale amperes
100
VIOUT(Q)VCC / VIOUT(Q)5V
VCC / 5 V
100
SensVCC / Sens5V
VCC / 5 V
‰
Output Voltage versus Sampled Current
Accuracy at 0 A and at Full-Scale Current
Increasing VIOUT
(V)
+IP (A)
Accuracy
Accuracy
Accuracy
25°C Only
Accuracy
25°C Only
Accuracy
25°C Only
Accuracy
0 A
vrOe $Temp erature
Average
VIOUT
–IP (A)
vrOe $Temp erature
vrOe $Temp erature
Decreasing VIOUT
(V)
IP(min)
IP(max)
Full Scale
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
10
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Power on Time versus External Filter Capacitance
0
20
40
60
80
100
120
140
160
180
200
01020304050
CF (nF)
CF (nF)
tPO (μs)
IP
=
5 A
IP
=
0 A
Noise versus External Filter Capacitance
1
1000
10
100
10000
0.01 0.1 1 10 100 1000
Noise
(p-p)
(mA)
Noise vs. Fi l t er Cap
400
350
300
250
200
150
100
50
0
05025 75 100 125 150
t
r
(μs)
CF (nF)
Rise Time versus External Filter CapacitanceRise Time versus External Filter Capacitance
0
200
400
600
800
1000
1200
0 100 200 300 400 500
t
r
(μs)
CF (nF)
Expanded in chart at right
}
Definitions of Dynamic Response Characteristics
Primary Current
Transducer Output
90
10
0
I (%)
Rise Time, trt
Rise time (tr). The time interval between a) when the device
reaches 10% of its full scale value, and b) when it reaches 90%
of its full scale value. The rise time to a step response is used to
derive the bandwidth of the device, in which ƒ(–3 dB) = 0.35 / tr.
Both tr and tRESPONSE are detrimentally affected by eddy current
losses observed in the conductive IC ground plane.
Excitation Signal
Output (mV)
15 A
Step Response
TA=25°C
CF (nF) tr (μs)
0 6.6
1 7.7
4.7 17.4
10 32.1
22 68.2
47 88.2
100 291.3
220 623.0
470 1120.0
Power-On Time (tPO). When the supply is ramped to its operat-
ing voltage, the device requires a finite time to power its internal
components before responding to an input magnetic field.
Power-On Time, tPO , is defined as the time it takes for the output
voltage to settle within ±10% of its steady state value under an
applied magnetic field, after the power supply has reached its
minimum specified operating voltage, VCC(min), as shown in the
chart at right.
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
11
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Chopper Stabilization is an innovative circuit technique that is
used to minimize the offset voltage of a Hall element and an asso-
ciated on-chip amplifier. Allegro patented a Chopper Stabiliza-
tion technique that nearly eliminates Hall IC output drift induced
by temperature or package stress effects. This offset reduction
technique is based on a signal modulation-demodulation process.
Modulation is used to separate the undesired DC offset signal
from the magnetically induced signal in the frequency domain.
Then, using a low-pass filter, the modulated DC offset is sup-
pressed while the magnetically induced signal passes through
the filter. As a result of this chopper stabilization approach, the
output voltage from the Hall IC is desensitized to the effects
of temperature and mechanical stress. This technique produces
devices that have an extremely stable Electrical Offset Voltage,
are immune to thermal stress, and have precise recoverability
after temperature cycling.
This technique is made possible through the use of a BiCMOS
process that allows the use of low-offset and low-noise amplifiers
in combination with high-density logic integration and sample
and hold circuits.
Chopper Stabilization Technique
Amp
Regulator
Clock/Logic
Hall Element
Sample and
Hold
Low-Pass
Filter
Concept of Chopper Stabilization Technique
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
12
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
+
–
IP+
IP+
IP–
IP–
IP
7
5
5
8
+5 V
U1
LMV7235
VIOUT VOUT
GND
6
2
4
4
1
1
2
3
3
FILTER
VCC
ACS712
D1
1N914
R2
100 kΩ
R1
33 kΩ
RPU
100 kΩ
Fault
CBYP
0.1 μF
CF
1 nF
+
–
IP+
IP+
IP–
IP–
7
5
8
+5 V
U1
LT1178
Q1
2N7002
VIOUT VOUT
VPEAK
VRESET
GND
6
2
4
1
3
D1
1N914
VCC
ACS712
R4
10 kΩ
R1
1 MΩ
R2
33 kΩ
RF
10 kΩ
R3
330 kΩ
CBYP
0.1 μF
C1
0.1 μF
COUT
0.1 μF
CF
1 nF
C2
0.1 μF
FILTER
IP
IP+
IP+
IP–
IP–
IP
7
5
8
+5 V
D1
1N4448W
VIOUT VOUT
GND
6
2
4
1
3FILTER
VCC
ACS712 R1
10 kΩ
CBYP
0.1 μF
RF
2 kΩ
CF
1 nF
C1
A-to-D
Converter
Typical Applications
Application 5. 10 A Overcurrent Fault Latch. Fault threshold set by R1 and
R2. This circuit latches an overcurrent fault and holds it until the 5 V rail is
powered down.
Application 2. Peak Detecting Circuit
Application 4. Rectified Output. 3.3 V scaling and rectification application
for A-to-D converters. Replaces current transformer solutions with simpler
ACS circuit. C1 is a function of the load resistance and filtering desired.
R1 can be omitted if the full range is desired.
+
–
IP+
IP+
IP–
IP–
IP
7
5
5
8
+5 V
LM321
VIOUT
VOUT
GND
6
2
4
1
14
2
3
3
FILTER
VCC
ACS712
R2
100 kΩ
R1
100 kΩ
R3
3.3 kΩ
CBYP
0.1 μF
CF
0.01 μF
C1
1000 pF
RF
1 kΩ
Application 3. This configuration increases gain to 610 mV/A
(tested using the ACS712ELC-05A).
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
13
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Improving Sensing System Accuracy Using the FILTER Pin
In low-frequency sensing applications, it is often advantageous
to add a simple RC filter to the output of the device. Such a low-
pass filter improves the signal-to-noise ratio, and therefore the
resolution, of the device output signal. However, the addition of
an RC filter to the output of a sensor IC can result in undesirable
device output attenuation — even for DC signals.
Signal attenuation, ∆VAT T , is a result of the resistive divider
effect between the resistance of the external filter, RF (see
Application 6), and the input impedance and resistance of the
customer interface circuit, RINTFC. The transfer function of this
resistive divider is given by:
Even if RF and RINTFC are designed to match, the two individual
resistance values will most likely drift by different amounts over
temperature. Therefore, signal attenuation will vary as a function
of temperature. Note that, in many cases, the input impedance,
RINTFC , of a typical analog-to-digital converter (ADC) can be as
low as 10 kΩ.
The ACS712 contains an internal resistor, a FILTER pin connec-
tion to the printed circuit board, and an internal buffer amplifier.
With this circuit architecture, users can implement a simple
RC filter via the addition of a capacitor, CF (see Application 7)
from the FILTER pin to ground. The buffer amplifier inside of
the ACS712 (located after the internal resistor and FILTER pin
connection) eliminates the attenuation caused by the resistive
divider effect described in the equation for ∆VAT T. Therefore, the
ACS712 device is ideal for use in high-accuracy applications
that cannot afford the signal attenuation associated with the use
of an external RC low-pass filter.
=
∆V
ATT
RINTFC
RF + RINTFC
V
IOUT
⎟
⎠
⎞
⎜
⎜
⎝
⎛
.
Application 6. When a low pass filter is constructed
externally to a standard Hall effect device, a resistive
divider may exist between the filter resistor, RF, and
the resistance of the customer interface circuit, RINTFC.
This resistive divider will cause excessive attenuation,
as given by the transfer function for VATT.
Application 7. Using the FILTER pin
provided on the ACS712 eliminates the
attenuation effects of the resistor divider
between RF and RINTFC, shown in Appli-
cation 6.
Application
Interface
Circuit
Resistive Divider
RINTFC
Low Pass Filter
RF
Amp Out
VCC
+5 V
Pin 8
Pin 7
VIOUT
Pin 6
N.C.
Input
GND
Pin 5
Filter
Dynamic Offset
Cancellation
IP+ IP+
0.1 MF
Pin 1 Pin 2
IP– IP–
Pin 3 Pin 4
Gain Temperature
Coefficient Offset
Voltage
Regulator
Trim Control
To all subcircuits
Input
VCC
Pin 8
Pin 7
VIOUT
GND
Pin 5 FILTER
Pin 6
Dynamic Offset
Cancellation
IP+
Pin 1
IP+
Pin 2
IP–
Pin 3
IP–
Pin 4
Sense
Trim
Signal
Recovery
Sense Temperature
Coefficient Trim
0 Ampere
Offset Adjust
Hall Current
Drive
+5 V
Application
Interface
Circuit
Buffer Amplifier
and Resistor
RINTFC
Allegro ACS712
Allegro ACS706
CF
1 nF
CF
1 nF
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
14
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Package LC, 8-pin SOIC
C
SEATING
PLANE
1.27 BSC
GAUGE PLANE
SEATING PLANE
ATerminal #1 mark area
B
Reference land pattern layout (reference IPC7351
SOIC127P600X175-8M); all pads a minimum of 0.20 mm from all
adjacent pads; adjust as necessary to meet application process
requirements and PCB layout tolerances
B
D
C
21
8
Branding scale and appearance at supplier discretion
C
SEATING
PLANE
C0.10
8X
0.25 BSC
1.04 REF
1.75 MAX
For Reference Only; not for tooling use (reference MS-012AA)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
4.90 ±0.10
3.90 ±0.10 6.00 ±0.20
0.51
0.31 0.25
0.10
0.25
0.17
1.27
0.40
8°
0°
N = Device part number
T = Device temperature range
P = Package Designator
A = Amperage
L = Lot number
Belly Brand = Country of Origin
NNNNNNN
LLLLL
1
TPP-AAA
A
Standard Branding Reference View
21
8
PCB Layout Reference View
C
0.65 1.27
5.60
1.75
Branded Face
Fully Integrated, Hall Ef fect-Based Linear Current Sensor IC
with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor
ACS712
15
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Copyright ©2006-2011, Allegro MicroSystems, Inc.
The products described herein are protected by U.S. patents: 5,621,319; 7,598,601; and patent pending.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to per-
mit improvements in the per for mance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the
information being relied upon is current.
Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
The in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use;
nor for any in fringe ment of patents or other rights of third parties which may result from its use.
For the latest version of this document, visit our website:
www.allegromicro.com
Revision History
Revision Revision Date Description of Revision
Rev. 14 October 12, 2011 Update branding specifications
