ACS712 [ALLEGRO]
Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor; 全集成，基于霍尔效应的线性电流传感器与2.1 kVRMS电压绝缘及低电阻电流导体
| 型号： | ACS712 |
| 厂家： | 
ALLEGRO MICROSYSTEMS |
| 描述： | Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor |
| 文件： | 总12页 (文件大小：668K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
ACS712
Fully Integrated, Hall Effect-Based Linear Current Sensor
with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
Features and Benefits
Description
The Allegro® ACS712 provides economical and precise
solutionsforACorDCcurrentsensinginindustrial,automotive,
commercial, and communications systems. The device
package allows for easy implementation by the customer.
Typical applications include motor control, load detection and
management, switched-mode power supplies, and overcurrent
fault protection.
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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
50 kHz bandwidth
Total output error 1.5% at TA= 25°C, and 4% at –40°C to 85°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
The device consists of a precise, low-offset, linear Hall
sensor 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 is sensed
by the integrated Hall IC and converted 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.
Package: 8 pin SOIC (suffix LC)
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 sensing. The internal resistance of
this conductive path is 1.2 mΩ typical, providing low power
Continued on the next page…
Approximate Scale 1:1
Typical Application
+5 V
8
7
1
2
VCC
IP+
IP+
VOUT
C
VIOUT
0.B1YPμF
IP
ACS712
6
5
3
4
FILTER
IP–
IP–
C
1FnF
GND
Application 1. The ACS712 outputs an analog signal, VOUT
that varies linearly with the uni- or bi-directional AC or DC
primary sensed current, IP, within the range specified. CF
is recommended for noise management, with values that
depend on the application.
.
ACS712-DS, Rev.1
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
Description (continued)
TheACS712 is provided in a small, surface mount SOIC8 package.
The leadframe is plated with 100% matte tin, which is compatible
withstandardlead(Pb)freeprintedcircuitboardassemblyprocesses.
Internally,thedeviceisPb-free,exceptforflip-chiphigh-temperature
Pb-based solder balls, currently exempt from RoHS. The device is
fully calibrated prior to shipment from the factory.
loss. The thickness of the copper conductor allows survival of
the device at up to 5× overcurrent conditions. The terminals of
the conductive path are electrically isolated from the sensor leads
(pins 5 through 8). This allows the ACS712 current sensor to be
used in applications requiring electrical isolation without the use
of opto-isolators or other costly isolation techniques.
Selection Guide
TOP
(°C)
Optimized Range, IP Sensitivity, Sens
Part Number
Packing*
(A)
(Typ) (mV/A)
ACS712ELCTR-05B-T Tape and reel, 3000 pieces/reel
ACS712ELCTR-20A-T Tape and reel, 3000 pieces/reel
ACS712ELCTR-30A-T Tape and reel, 3000 pieces/reel
*Contact Allegro for additional packing options.
–40 to 85
–40 to 85
–40 to 85
±5
185
100
66
±20
±30
Absolute Maximum Ratings
Characteristic
Symbol
VCC
Notes
Rating
8
Units
V
Supply Voltage
Reverse Supply Voltage
Output Voltage
VRCC
–0.1
8
V
VIOUT
V
Reverse Output Voltage
Output Current Source
Output Current Sink
VRIOUT
IIOUT(Source)
IIOUT(Sink)
–0.1
3
V
mA
mA
10
100 total pulses, 250 ms duration each, applied
at a rate of 1 pulse every 100 seconds.
Overcurrent Transient Tolerance
IP
60
A
Maximum Transient Sensed Current
Nominal Operating Ambient Temperature
Maximum Junction
IR(max)
TA
Junction Temperature, TJ < TJ(max)
Range E
60
–40 to 85
165
A
ºC
ºC
TJ(max)
Tstg
Storage Temperature
–65 to 170
ºC
Parameter
Fire and Electric Shock
Specification
TÜV America
CAN/CSA-C22.2 No. 60950-1-03
UL 60950-1:2003
Certificate Number:
U8V 06 05 54214 010
EN 60950-1:2001
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
2
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
Functional Block Diagram
+5 V
VCC
(Pin 8)
Hall Current
Drive
IP+
Sense Temperature
Coefficient Trim
(Pin 1)
IP+
(Pin 2)
Signal
VIOUT
(Pin 7)
Recovery
R
F(INT)
IP−
(Pin 3)
Sense
Trim
IP−
0 Ampere
Offset Adjust
(Pin 4)
GND
(Pin 5)
FILTER
(Pin 6)
Pin-out Diagram
IP+
IP+
IP–
IP–
1
2
3
4
8
7
6
5
VCC
VIOUT
FILTER
GND
Terminal List Table
Number
Name
Description
1 and 2
IP+
Terminals for current being sensed; fused internally
Terminals for current being sensed; fused internally
Signal ground terminal
3 and 4
IP–
5
6
7
8
GND
FILTER
VIOUT
VCC
Terminal for external capacitor that sets bandwidth
Analog output signal
Device power supply terminal
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
3
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
COMMON OPERATING CHARACTERISTICS1 over full range of TOP, 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
6
5.0
8
5.5
11
–
V
mA
V
Supply Current
ICC
VZ
VCC = 5.0 V, output open
ICC = 11 mA, TA = 25°C
IIOUT = 1.2 mA, TA=25°C
VIOUT to GND
Output Zener Clamp Voltage
Output Resistance
6
8.3
1
RIOUT
CLOAD
RLOAD
–
2
Ω
Output Capacitance Load
Output Resistive Load
–
–
10
–
nF
kΩ
mΩ
V
VIOUT to GND
4.7
–
–
Primary Conductor Resistance RPRIMARY TA = 25°C
1.2
–
–
RMS Isolation Voltage
DC Isolation Voltage
Propagation Time
Response Time
Rise Time
VISORMS Pins 1-4 and 5-8; 60 Hz, 1 minute, TA=25°C
2100
–
–
VISODC
tPROP
Pins 1-4 and 5-8; 1 minute, TA=25°C
IP = IP(max), TA = 25°C, COUT = open
5000
3
–
V
–
–
μs
μs
μs
kHz
%
tRESPONSE IP = IP(max), TA = 25°C, COUT = open
–
7
–
tr
f
IP = IP(max), TA = 25°C, COUT = open
–3 dB, TA = 25°C; IP is 10 A peak-to-peak
Over full range of IP
–
5
–
Frequency Bandwidth
Nonlinearity
50
–
–
–
ELIN
ESYM
±1
100
±1.5
102
Symmetry
Over full range of IP
98
%
VCC
0.5
×
Zero Current Output Voltage
Magnetic Offset Error
VIOUT(Q) Bidirectional; IP = 0 A, TA = 25°C
VERROM IP = 0 A, after excursion of 5 A
VCH
–
–
–
–
V
0
mV
mV
VCC
0.9375
×
Typ.–110
Typ.+110
Clamping Voltage
Power-On Time
VCC
0.0625
×
VCL
Typ.–110
Typ.+110
mV
Output reaches 90% of steady-state level, TJ =25°C, 20 A present
on leadframe
tPO
–
–
35
–
–
ꢀs
Magnetic Coupling2
12
G/A
Internal Filter Resistance3
RF(INT)
1.7
kꢁ
1Device may be operated at higher primary current levels, IP, and ambient, TA, and internal leadframe temperatures, TOP, 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.
–40
Typ.
–
Max.
85
Units
°C
Operating Internal Leadframe Temperature
TOP E range
Value
5
Units
°C/W
Junction-to-Lead Thermal Resistance2
Junction-to-Ambient Thermal Resistance
RθJL Mounted on the Allegro ASEK 712 evaluation board
Mounted on the Allegro 85-0322 evaluation board, includes the power con-
sumed by the board
RθJA
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.
Allegro MicroSystems, Inc.
4
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
x05A PERFORMANCE CHARACTERISTICS TOP = –40°C to 85°C1, CF = 1 nF, and VCC = 5 V, unless otherwise specified
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
5
Units
A
Optimized Accuracy Range
IP
–5
–
SensTA
Over full range of IP, TA = 25°C
–
185
–
–
mV/A
mV/A
Sensitivity2
Noise
SensTOP Over full range of IP
178
193
Peak-to-peak, TA= 25°C, 185 mV/A programmed Sensitivity,
CF =4.7 nF, COUT = open, 20 kHz bandwidth
–
–
–
45
20
75
–
–
–
mV
mV
mV
Peak-to-peak, TA = 25°C, 185 mV/A programmed Sensitivity,
CF = 47 nF, COUT = open, 2 kHz bandwidth
VNOISE(PP)
Peak-to-peak, TA = 25°C, 185 mV/A programmed Sensitivity,
CF = 1 nF, COUT = open, 50 kHz bandwidth
Electrical Offset Voltage
Total Output Error3
VOE
IP = 0 A
–40
–
–
40
–
mV
%
ETOT
IP =±5 A, TA = 25°C
±1.5
1Device may be operated at higher primary current levels, IP, and ambient temperatures, TOP, provided that the Maximum Junction Temperature,
J(max), is not exceeded.
T
2At –40°C Sensitivity may shift as much 9% outside of the datasheet limits.
3Percentage of IP, with IP = 5 A. Output filtered.
x20A PERFORMANCE CHARACTERISTICS TOP = –40°C to 85°C1, CF = 1 nF, and VCC = 5 V, unless otherwise specified
Characteristic
Symbol
Test Conditions
Min.
–20
–
Typ.
Max.
20
Units
A
Optimized Accuracy Range
IP
–
SensTA
Over full range of IP, TA = 25°C
100
–
–
mV/A
mV/A
Sensitivity2
Noise
SensTOP Over full range of IP
97
103
Peak-to-peak, TA= 25°C, 100 mV/A programmed Sensitivity,
CF =4.7 nF, COUT = open, 20 kHz bandwidth
–
–
–
24
10
40
–
–
–
mV
mV
mV
Peak-to-peak, TA = 25°C, 100 mV/A programmed Sensitivity,
CF = 47 nF, COUT = open, 2 kHz bandwidth
VNOISE(PP)
Peak-to-peak, TA = 25°C, 100 mV/A programmed Sensitivity,
CF = 1 nF, COUT = open, 50 kHz bandwidth
Electrical Offset Voltage
Total Output Error3
VOE
IP = 0 A
–30
–
–
30
–
mV
%
ETOT
IP =±20 A, TA = 25°C
±1.5
1Device may be operated at higher primary current levels, IP, and ambient temperatures, TOP, provided that the Maximum Junction Temperature,
TJ(max), is not exceeded.
2At –40°C Sensitivity may shift as much 9% outside of the datasheet limits.
3Percentage of IP, with IP = 20 A. Output filtered.
x30A PERFORMANCE CHARACTERISTICS TOP = –40°C to 85°C1, CF = 1 nF, and VCC = 5 V, unless otherwise specified
Characteristic
Symbol
Test Conditions
Min.
–30
–
Typ.
Max.
30
Units
A
Optimized Accuracy Range
IP
–
SensTA
Over full range of IP, TA = 25°C
66
–
–
mV/A
mV/A
Sensitivity2
Noise
SensTOP Over full range of IP
64
68
Peak-to-peak, TA= 25°C, 66 mV/A programmed Sensitivity,
CF =4.7 nF, COUT = open, 20 kHz bandwidth
–
–
–
20
7
–
–
–
mV
mV
mV
Peak-to-peak, TA = 25°C, 66 mV/A programmed Sensitivity,
CF = 47 nF, COUT = open, 2 kHz bandwidth
VNOISE(PP)
Peak-to-peak, TA = 25°C, 66 mV/A programmed Sensitivity,
CF = 1 nF, COUT = open, 50 kHz bandwidth
35
Electrical Offset Voltage
Total Output Error3
VOE
IP = 0 A
–30
–
–
30
–
mV
%
ETOT
IP = ±30 A, TA = 25°C
±1.5
1Device may be operated at higher primary current levels, IP, and ambient temperatures, TOP, provided that the Maximum Junction Temperature,
TJ(max), is not exceeded.
2At –40°C Sensitivity may shift as much 9% outside of the datasheet limits.
3Percentage of IP, with IP = 30 A. Output filtered.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
5
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
Characteristic Performance
IP = 5 A, Sens = 185 mV/A unless otherwise specified
Mean Supply Current versus Ambient Temperature
Supply Current versus Supply Voltage
VCC = 5 V
10.5
10.0
9.5
9.0
8.5
8.0
7.5
7.0
6.5
10.3
10.1
9.9
9.7
9.5
9.3
9.1
8.9
8.7
8.5
6.0
-50
4.5 4.6 4.7 4.8 4.9
5
5.1 5.2 5.3 5.4 5.5
0
50
100
A (°C)
150
200
V
CC (V)
T
Magnetic Offset versus Ambient Temperature
Nonlinearity versus Ambient Temperature
IP = 10 A
2.0
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
-50
0
50
100
TA (°C)
150
200
-50
0
50
100
TA (°C)
150
200
Mean Total Output Error versus Ambient Temperature
IP = 10 A
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-50
0
50
100
TA (°C)
150
200
Output Voltage versus Sensed Current
Sensitivity versus Sensed Current
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
188.0
186.0
184.0
182.0
180.0
178.0
176.0
TA (°C)
TA (°C)
150
85
85
25
-40
25
-40
-10 -8 -6 -4 -2
0
2
4
6
8
10
-10 -8 -6 -4 -2
0
2
4
6
8
10
Ip (A)
Ip (A)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
6
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
Characteristic Performance
IP = 30 A, Sens = 66 mV/A unless otherwise specified
Mean Supply Current versus Ambient Temperature
Supply Current versus Supply Voltage
VCC = 5 V
10.5
10.0
9.5
9.0
8.5
8.0
7.5
7.0
6.5
10.3
10.1
9.9
9.7
9.5
9.3
9.1
8.9
8.7
8.5
6.0
-50
4.5 4.6 4.7 4.8 4.9
5
5.1 5.2 5.3 5.4 5.5
0
50
100
TA (°C)
150
200
V
CC (V)
Magnetic Offset Current versus Ambient Temperature
Nonlinearity versus Ambient Temperature
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1.00
0.80
0.60
0.40
0.20
0
-50
0
50
100
TA (°C)
150
200
-50
0
50
100
TA (°C)
150
200
Mean Total Output Error versus Ambient Temperature
5.0
4.0
3.0
2.0
1.0
0.0
-1.0
-2.0
-3.0
-4.0
-5.0
-50
0
50
100
TA (°C)
150
200
Output Voltage versus Sensed Current
Sensitivity versus Sensed Current
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
75.0
70.0
65.0
60.0
55.0
50.0
TA (°C)
TA (°C)
150
85
85
25
-40
25
-40
-30
-20
-10
0
10
20
30
-30
-20
-10
0
10
20
30
Ip (A)
Ip (A)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
7
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
Definitions of Accuracy Characteristics
Sensitivity (Sens). The change in sensor output in response to a
1A 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.
Accuracy is divided into four areas:
• 0 A at 25°C. Accuracy of sensing zero current flow at 25°C,
without the effects of temperature.
• 0 A over Δ temperature. Accuracy of sensing zero current
flow including temperature effects.
• Full-scale current at 25°C. Accuracy of sensing the full-scale
current at 25°C, without the effects of temperature.
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.
• Full-scale current over Δ temperature. Accuracy of sensing 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
Linearity (ELIN). The degree to which the voltage output from
the sensor varies in direct proportion to the primary current
through its full-scale amplitude. Nonlinearity in the output can be
attributed to the saturation of the flux concentrator approaching
the full-scale current. The following equation is used to derive the
linearity:
proportional to its supply voltage, VCC.The following formula is
used to derive the ratiometric change in 0 A output voltage,
ΔVIOUT(Q)RAT (%).
V
IOUT(Q)VCC / VIOUT(Q)5V
100
VCC
/
5 V
V
– VIOUT(Q)
) [ {
Δ gain × % sat (
IOUT_full-scale amperes
2 (VIOUT_half-scale amperes – VIOUT(Q)
100
1–
The ratiometric change in sensitivity, ΔSensRAT (%), is defined as:
{
[
)
SensVCC / Sens5V
where VIOUT_full-scale amperes = the output voltage (V) when the
sensed current approximates full-scale ±IP .
100
VCC
/
5 V
‰
ꢀ
Symmetry (ESYM). The degree to which the absolute voltage
output from the sensor varies in proportion to either a positive
or negative full-scale primary current. The following formula is
used to derive symmetry:
Output Voltage versus Sensed Current
Accuracy at 0 A and at Full-Scale Current
Increasing VIOUT(V)
Accuracy
Over $Temp erature
VIOUT_+ full-scale amperes – VIOUT(Q)
100
V
IOUT(Q) – VIOUT_–full-scale amperes
Accuracy
25°C Only
Quiescent output voltage (VIOUT(Q)). The output of the sensor
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.
Average
V
IOUT
Accuracy
Over $Temp erature
Accuracy
25°C Only
IP(min)
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.
–IP (A)
+IP (A)
Full Scale
I
P(max)
0 A
Accuracy (ETOT). The accuracy represents the maximum devia-
tion of the actual output from its ideal value. This is also known
as the total ouput error. The accuracy is illustrated graphically in
the output voltage versus current chart at right.
Accuracy
25°C Only
Accuracy
Over $Temp erature
Decreasing VIOUT(V)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
8
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
Definitions of Dynamic Response Characteristics
Primary Current
I (%)
90
Propagation delay (tPROP). The time required for the sensor
output to reflect a change in the primary current signal. Propaga-
tion delay is attributed to inductive loading within the linear IC
package, as well as in the inductive loop formed by the primary
conductor geometry. Propagation delay can be considered as a
fixed time offset and may be compensated.
Transducer Output
0
t
Propagation Time, tPROP
Primary Current
I (%)
90
Response time (tRESPONSE). The time interval between
a) when the primary current signal reaches 90% of its final
value, and b) when the sensor reaches 90% of its output
corresponding to the applied current.
Transducer Output
0
t
Response Time, t
Primary Current
RESPONSE
Rise time (tr). The time interval between a) when the sensor
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 current sensor, 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.
I (%)
90
Transducer Output
10
0
t
Rise Time, t
r
Step Response
TA=25°C
Power on Time versus External Filter Capacitance
200
180
160
140
120
100
80
IP=5 A
IP=0 A
60
40
20
0
Output (mV)
0
10
20
30
40
50
C
F (nF)
Noise vs. Filter Cap
Noise versus External Filter Capacitance
15 A
10000
1000
100
Excitation Signal
10
1
0.01
0.1
1
10
100
1000
CF (nF)
Rise Time versus External Filter Capacitance
Rise Time versus External Filter Capacitance
CF (nF)
tr (μs)
400
350
300
250
200
150
0
1200
0
1
4.7
10
22
47
100
220
470
6.6
7.7
17.4
32.1
68.2
88.2
291.3
623.0
1120.0
1000
800
600
400
200
0
Expanded in chart at right
}
0
100
200
300
400
500
0
50
75
100
125
150
CF (nF)
CF (nF)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
9
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
Chopper Stabilization Technique
Chopper Stabilization is an innovative circuit technique that is
This technique is made possible through the use of a BiCMOS
used to minimize the offset voltage of a Hall element and an asso- process that allows the use of low-offset and low-noise amplifiers
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 suppressed
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 tempera-
ture 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.
in combination with high-density logic integration and sample
and hold circuits.
Regulator
Clock/Logic
Low-Pass
Filter
Hall Element
Amp
Concept of Chopper Stabilization Technique
Typical Applications
+5 V
+5 V
VPEAK
CBYP
0.1 μF
R1
CBYP
0.1 μF
C2
100 kΩ
0.1 μF
VRESET
R4
Q1
2N7002
10 kΩ
R2
COUT
8
7
100 kΩ
LM321
4
1
3
1
+
–
VCC
5
2
0.1 μF
8
7
IP+
VOUT
1
2
VCC
VOUT
+
–
IP+
IP+
2
VIOUT
IP+
VIOUT
RF
10 kΩ
IP
RF
1 kΩ
ACS712
U1
D1
R1
1 MΩ
CF
C1
IP
ACS712
6
5
LT1178 1N914
3
4
1000 pF
FILTER
R3
6
5
IP–
IP–
3
4
FILTER
3.3 kΩ
IP–
IP–
CF
0.01 μF
1 nF
GND
C1
R3
GND
R2
33 kΩ
0.1 μF
330 kΩ
Application 3. This configuration increases gain to 610 mV/A
(tested using the ACS712ELC-05A).
Application 2. Peak Detecting Circuit
+5 V
+5 V
CBYP
0.1 μF
R1
33 kΩ
CBYP
0.1 μF
RPU
R2
100 kΩ
100 kΩ
8
7
8
1
2
VCC
1
D1
VCC
IP+
IP+
IP+
VOUT
1N4448W
4
3
VOUT
7
5
2
2
A-to-D
Converter
VIOUT
–
+
Fault
VIOUT
IP+
1
RF
IP
ACS712
ACS712
IP
2 kΩ
U1
R1
10 kΩ
CF
1 nF
6
5
3
4
C1
6
5
LMV7235
FILTER
3
4
IP–
IP–
FILTER
GND
CF
IP–
IP–
1 nF
GND
D1
1N914
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.
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.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
10
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
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 sensor. Such a low-
pass filter improves the signal-to-noise ratio, and therefore the
resolution, of the sensor output signal. However, the addition of
an RC filter to the output of a sensor IC can result in undesirable
sensor output attenuation — even for dc signals.
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 kꢀ.
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 ∆VATT. 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.
Signal attenuation, ∆VATT , 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:
RINTFC
⎛
⎞
.
∆VATT
V
⎜
⎜
=
IOUT
⎟
RF + RINTFC
⎝
⎠
Even if RF and RINTFC are designed to match, the two individual
resistance values will most likely drift by different amounts over
+5 V
Pin 3 Pin 4
VCC
Pin 8
IP–
IP–
Allegro ACS706
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,
Voltage
Regulator
To all subcircuits
.
VIOUT
Pin 7
Resistive Divider
Input
RF
Amp
Out
Application
Interface
Circuit
as given by the transfer function for ∆VATT
.
N.C.
Pin 6
0.1 MF
Low Pass Filter
Temperature
Coefficient
Gain
Offset
CF
1 nF
RINTFC
Trim Control
GND
Pin 5
IP+
Pin 1 Pin 2
IP+
+5 V
VCC
Pin 8
Allegro ACS712
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.
Hall Current
Drive
IP+
Sense Temperature
Coefficient Trim
Pin 1
IP+
Pin 2
Buffer Amplifier
and Resistor
Signal
Recovery
VIOUT
Pin 7
Input
Application
Interface
Circuit
IP–
Pin 3
Sense
Trim
IP–
Pin 4
0 Ampere
Offset Adjust
RINTFC
GND
Pin 5
FILTER
Pin 6
CF
1 nF
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
11
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Fully Integrated, Hall Effect-Based Linear Current Sensor with
2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor
ACS712
6.20 .244
5.80 .228
Package LC, 8-pin SOIC
0.25 [.010] M B M
5.00 .197
4.80 .189
8º
0º
A
B
8
0.25 .010
0.17 .007
Preliminary dimensions, for reference only
Dimensions in millimeters
U.S. Customary dimensions (in.) in brackets, for reference only
4.00 .157
3.80 .150
(reference JEDEC MS-012 AA)
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
Terminal #1 mark area
1.27 .050
0.40 .016
A
A
1
2
0.25 .010
C
8X
SEATING PLANE
GAUGE PLANE
SEATING
PLANE
0.10 [.004]
C
0.51 .020
0.31 .012
0.25 [.010] M
1.75 .069
1.35 .053
8X
C A B
0.25 .010
0.10 .004
1.27 .050
1
2
3
4
8
7
6
5
Package Branding
Two alternative patterns are used
ACS
712
T
Allegro Current Sensor
Device family number
ACS
712
T
Allegro Current Sensor
Device family number
Indicator of 100% matte tin leadframe plating
Operating ambient temperature range code
Package type designator
Indicator of 100% matte tin leadframe plating
Operating ambient temperature range code
Package type designator
ACS712T
RLCPPP
L...L
ACS712T
RLCPPP
YYWWA
R
R
LC
PPP
YY
WW
A
LC
Primary sensed current
PPP
L...L
YY
Primary sensed current
YYWW
Date code: Calendar year (last two digits)
Date code: Calendar week
Lot code
Date code: Calendar year (last two digits)
Date code: Calendar week
Date code: Shift code
WW
The products described herein are manufactured under one or more
of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283;
or manufacturability of its products. Before placing an order,
the user is cautioned to verify that the information being relied
5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719; upon is current. The information included herein is believed to
5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents
pending.
be accurate and reliable. However, Allegro MicroSystems, Inc.
assumes no responsibility for its use; nor for any infringement of
patents or other rights of third parties which may result from its
use.
Allegro MicroSystems, Inc. reserves the right to make, from time
to time, such departures from the detail specifications as may be
required to permit improvements in the performance, reliability,
Copyright ©2006, Allegro MicroSystems, Inc.
For the latest version of this document, go to our website at:
www.allegromicro.com
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
12
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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