ACS704ELC-005
Fully Integrated, Hall Effect-Based Linear Current Sensor
with Voltage Isolation and a Low-Resistance Current Conductor
Not for New Design
These parts are in production but have been determined to be
NOT FOR NEW DESIGN. This classification indicates that sale of
this device is currently restricted to existing customer applications.
The device should not be purchased for new design applications
because obsolescence in the near future is probable. Samples are no
longer available.
Date of status change: October 31, 2006
Recommended Substitutions:
For existing customer transition, and for new customers or new applications, refer to the ACS712.
NOTE: For detailed information on purchasing options, contact your
local Allegro field applications engineer or sales representative.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The
information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
ACS706ELC-20A
Bidirectional 1.5 mΩ Hall Effect Based Linear Current Sensor
with Voltage Isolation and 20 A Dynamic Range
The Allegro ACS706 family of current sensors provides economical and
precise solutions for current sensing in industrial, 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.
Package LC
Pin 8: VCC
Pin 7: VOUT
Pin 6: N.C.
Pin 5: GND
Pin 1: IP+
Pin 2: IP+
Pin 3: IP–
Pin 4: IP–
Pins 6 and 7 are internally connected in shipping
product. For compatibility with future devices,
leave pin 6 floating.
Nominal Operating Temperature, TA
Range E............................................ –40 to 85ºC
Overcurrent Transient Tolerance*, IP ................ 60 A
*100
total pulses, 250 ms duration each, applied at a rate of
1 pulse every 100 seconds.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC .......................................... 16 V
Reverse Supply Voltage, VRCC ........................ –16 V
Output Voltage, VOUT ........................................ 16 V
Reverse Output Voltage, VROUT...................... –0.1 V
Output Current Source, IOUT(Source) ................. 3 mA
Output Current Sink, IOUT(Sink) .......................10 mA
Maximum Transient Sensed Current*, IR(max) ... 100 A
Operating Temperature,
Maximum Junction, TJ(max)....................... 165°C
Storage Temperature, TS ...................... –65 to 170°C
*Junction
Temperature, TJ < TJ(max).
TÜV America
Certificate Number:
U8V 04 12 54214 005
ACS706ELC20A-DS, Rev. 2
The device consists of a precision, 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 at the
factory.
The output of the device has a positive slope (>VCC / 2) 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 typically 1.5 mΩ, providing low power loss. The thickness
of the copper conductor allows survival of the device at up to 3× overcurrent
conditions. The terminals of the conductive path are electrically isolated from the
sensor leads (pins 5 through 8). This allows the ACS706 family of sensors to be
used in applications requiring electrical isolation without the use of opto-isolators
or other costly isolation techniques.
The ACS706 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 flip-chip uses high-temperature Pb-based solder balls, currently exempt from RoHS. The device is fully
calibrated prior to shipment from the factory.
Features and Benefits
• Small footprint, low-profile SOIC8 package
•
•
•
•
•
•
•
•
•
•
•
1.5 mΩ internal conductor resistance
Excellent replacement for sense resistors
1600 VRMS minimum isolation voltage between pins 1-4 and 5-8
4.5 to 5.5 V, single supply operation
50 kHz bandwidth
100 mV/A output sensitivity and 20 A dynamic range
Output voltage proportional to ac and dc currents
Factory-trimmed for accuracy
Extremely stable output offset voltage
Near-zero magnetic hysteresis
Ratiometric output from supply voltage
Use the following complete part number when ordering:
Part Number
Package
ACS706ELC-20A
SOIC8 surface mount
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Functional Block Diagram
+5 V
Pin 3 Pin 4
IP–
IP–
VCC
Pin 8
Voltage
Regulator
Filter
Dynamic Offset
Cancellation
To all subcircuits
Amp
VOUT
Pin 7
Out
A
N.C.
Pin 6
Gain
Temperature
Coefficient
0.1 μF
Offset
Trim Control
IP+
IP+
Pin 1 Pin 2
GND
Pin 5
A Pins 6 and 7 are internally connected in shipping product.
For compatibility with future devices, leave pin 6 floating.
2
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
OPERATING CHARACTERISTICS
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
IP
–20
–
20
A
IR
–20
–
20
A
VCC
4.5
5.0
5.5
V
mA
ELECTRICAL CHARACTERISTICS, over operating ambient temperature range unless otherwise specified
Optimized Accuracy Range
Linear Sensing Range
Supply Voltage
Supply Current
VCC = 5.0 V, output open
5
8
10
Output Resistance
ROUT
IOUT = 1.2 mA
–
1
2
Ω
Output Capacitance Load
CLOAD
VOUT to GND
–
–
10
nF
RLOAD
VOUT to GND
4.7
–
–
kΩ
–
1.5
–
mΩ
1600
2500
–
V
–
5000
–
V
3.15
–
μs
μs
Output Resistive Load
ICC
Primary Conductor Resistance
RPRIMARY
TA = 25°C
RMS Isolation Voltage
VISORMS
Pins 1-4 and 5-8; 60 Hz, 1 minute
DC Isolation Voltage
VISODC
PERFORMANCE CHARACTERISTICS, over operating ambient temperature range unless otherwise specified
Propagation Time
Response Time
tPROP
IP = ±20 A, TA = 25°C
–
tRESPONSE
IP = ±20 A, TA = 25°C
–
6
–
Rise Time
tr
IP = ±20 A, TA = 25°C
–
6.56
–
μs
Frequency Bandwidth
f
–3 dB, TA = 25°C; IP is 10 A peak-to-peak; no external filter
–
50
–
kHz
Over full range of IP , IP applied for 5 ms; TA = 25°C
–
100
–
mV/A
Over full range of IP , IP applied for 5 ms
94
–
106
mV/A
Sensitivity
Noise
Sens
VNOISE
Peak-to-peak, TA = 25°C, no external filter
–
70
–
mV
Root Mean Square, TA = 25°C, no external filter
–
12.5
–
mV
Linearity
ELIN
Over full range of IP , IP applied for 5 ms
–
±1
±3.5
%
Symmetry
ESYM
Over full range of IP , IP applied for 5 ms
98
100
102
%
IP = 0 A, TA = 25°C
–
VCC / 2
–
V
IP = 0 A, TA = 25°C
–15
–
15
mV
IP = 0 A
mV
Zero Current Output Voltage
Electrical Offset Voltage
Magnetic Offset Error
Total Output Error1
VOUT(Q)
VOE
IERROM
ETOT
–50
–
50
IP = 0 A, after excursion of 20 A
–
±0.01
±0.05
A
IP = ±20 A , IP applied for 5 ms; TA = 25°C
–
±1.5
–
%
IP = ±20 A , IP applied for 5 ms
–
–
±8.4
%
THERMAL CHARACTERISTICS2,3, TA = –40°C to 125°C, VCC = 5 V unless otherwise specified
Junction-to-Lead Thermal
Resistance
RθJL
Mounted on the Allegro ASEK 70x evaluation board; additional
information about reference boards and tests is available on the
Allegro Web site
Junction-to-Ambient Thermal
Resistance
RθJA
Mounted on the Allegro ASEK 70x evaluation board; additional
information about reference boards and tests is available on the
Allegro Web site
–
Value
–
Units
–
5
–
°C/W
–
41
–
°C/W
1Percentage
of IP, with IP = 20 A. Output filtered. Up to a 2.0% shift in ETOT may be observed at end-of-life for this device.
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 connecting the layers. Performance values include the power consumed by the PWB. Further details on the board are available from the ACS704 Frequently
Asked Questions document on our website. Further information about board design and thermal performance also can be found on pages 16 and 17 of
this datasheet.
3R
θJA values shown in this table are typical values, measured on the Allegro evaluation board. The actual thermal performance depends on the board
design, the airflow in the system, and thermal interactions between the sensor and surrounding components through the PCB and the ambient air. To
improve thermal performance, see our applications material on the Allegro Web site.
2 The Allegro
3
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Typical Performance Characteristics
Supply Current versus Ambient Temperature
VCC = 5 V
10.0
9.5
ICC (mA)
9.0
8.5
8.0
7.5
7.0
6.5
6.0
-50
-25
0
25
50
75
100
125
150
TA (°C)
Supply Current versus Applied VCC
8.66
8.64
8.62
ICC (mA)
8.60
8.58
8.56
8.54
8.52
8.50
8.48
8.46
8.44
4.5
4.6
4.7
4.8
4.9
5
5.1
5.2
5.3
5.4
5.5
VCC (V)
4
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Output Voltage versus Primary Current
VCC = 5 V
5.0
4.5
4.0
VOUT (V)
3.5
3.0
2.5
°C
–40
2.0
–20
1.5
25
85
1.0
150
0.5
0
–25
–20
–15
–10
–5
0
5
10
15
20
25
IP (A)
Sensitivity versus Primary Current
VCC = 5 V
110
°C
–40
–20
25
85
150
108
106
Sens (mV/A)
104
102
100
98
96
94
92
90
–25
–20
–15
–10
–5
0
5
10
15
20
25
IP (A)
5
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Zero Current Output Voltage vs. Ambient Temperature
IP = 0 A
2.525
2.520
VOUT(Q) (V)
2.515
2.510
2.505
2.500
2.495
2.490
2.485
2.480
2.475
-50
-25
0
25
50
75
100
125
150
TA (°C)
Zero Current Output Currrent versus Ambient Temperature
(Data in above chart converted to amperes)
IP = 0 A
0.25
0.20
IVOUT(Q) (A)
0.15
0.10
0.05
0
-0.05
-0.10
-0.15
-0.20
-0.25
-50
-25
0
25
50
75
100
125
150
TA (°C)
6
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Magnetic Offset versus Ambient Temperature
VOM (mA)
VCC = 5 V; IP = 0 A, after excursion to 20 A
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
TA (°C)
75
100
125
150
Nonlinearity versus Ambient Temperature
VCC = 5 V IP = 20 A
1.0
0.8
0.6
ELIN (%)
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–50
–25
0
25
50
75
100
125
150
TA (°C)
7
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Typical Percentage Error versus Ambient Temperature
Measurements at TA = –40, –20, 25, 85, and 125°C
8
6
ETOT (% of 20 A)
4
2
0
–2
–4
Mean + 3 Sigma
Mean
Mean – 3 Sigma
–6
–8
–50
–25
0
25
50
TA (°C)
75
100
125
150
TA (°C)
8
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Step Response of ACS706ELC-20A at TA=25°C
ACS706 Output (mV)
5 A Excitation Signal
Time = 5 μs/div.
Excitation signal = 1.00 A/div.
Output = 100 mV/div.
Typical Peak-to-Peak Noise of ACS706ELC-20A at TA=25°C
Time = 20 μs/div.
Noise = 20.0 mV/div.
9
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
ACS706ELC-20A Noise Filtering and Frequency Response Performance
Nominal
Programmed
Sensitivity
(mV/A)
Filtered
Peak-toPeak Noise
(mV)
Resistance
(kΩ)
Capacitance
(μF)
Unfiltered
–
–
70.0
0.700
6.56
80
0.200
58.8
0.588
7.82
50
0.320
49.9
0.499
9.55
40
0.392
46.3
0.463
10.25
20
0.800
32.9
0.329
16.15
21.9
0.219
30.14
13.3
0.133
53.29
9.8
0.098
79.73
10
1.6
7.0
3.15
3.3
4.8
0.01
100
Resolution
with Filtering
(A)
Rise Time
for 5A Step,
Filtered
(μs)
Break Frequency
of Filter on Output
(kHz)
0.6
26
1.3
0.013
394.66
0.3
53
0.58
0.00583
724.73
10
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Definitions of Accuracy Characteristics
Sensitivity (Sens). The change in sensor 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 programmed 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 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:
{ [
100 1–
(Vout_full-scale amperes – VOUT(Q) )
2 (Vout_half-scale amperes – VOUT(Q) )
[{
where Vout_full-scale amperes = the output voltage (V) when the sensed current approximates full-scale ±IP .
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:
100
Vout_+full-scale amperes – VOUT(Q)
VOUT(Q) –Vout_–full-scale amperes
Quiescent output voltage (VOUT(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 VOUT(Q) = 2.5 V. Variation in VOUT(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 output 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 deviation 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 on the following page.
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.
• 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, VOUT(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, ΔVOUT(Q)RAT (%):
100
VOUT(Q)VCC / VOUT(Q)5V
‰
VCC / 5 V
The ratiometric change in sensitivity, ΔSensRAT (%), is defined as:
100
SensVCC / Sens5V
‰
VCC / 5 V
11
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Output voltage vs. current, illustrating sensor accuracy at 0 A and at full-scale current
Increasing VOUT (V)
Accuracy
Over ΔTemperature
Accuracy
25°C Only
Average
VOUT
Accuracy
Over ΔTemperature
Accuracy
25°C Only
–IP (A)
–IP
IP
+IP (A)
Full Scale
0A
Accuracy
25°C Only
Accuracy
Over ΔTemperature
Decreasing VOUT (V)
12
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Definitions of Dynamic Response Characteristics
Propagation delay (tPROP): The time required for the sensor output to reflect a change in the primary current signal. Propagation 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.
I (%)
Primary Current
90
Transducer Output
0
Propagation Time, tPROP
t
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.
I (%)
Primary Current
90
Transducer Output
0
Response Time, tRESPONSE
t
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 (%)
Primary Current
90
Transducer Output
10
0
Rise Time, tr
t
13
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Standards and Physical Specifications
Parameter
Specification
Flammability (package molding compound)
UL recognized to UL 94V-0
Fire and Electric Shock
UL60950-1:2003
EN60950-1:2001
CAN/CSA C22.2 No. 60950-1:2003
Device Branding Key (Two alternative styles are used)
ACS706T
ELC20A
YYWWA
ACS
Allegro Current Sensor
704
Device family number
T
Indicator of 100% matte tin leadframe plating
E
Operating ambient temperature range code
LC
Package type designator
20A
Primary sensed current
YY
Manufacturing date code: Calendar year (last two digits)
WW
Manufacturing date code: Calendar week
A
ACS706T
ELC20A
L...L
YYWW
Manufacturing date code: Shift code
ACS
Allegro Current Sensor
704
Device family number
T
Indicator of 100% matte tin leadframe plating
E
Operating ambient temperature range code
LC
Package type designator
20A
Primary sensed current
L...L
Manufacturing lot code
YY
Manufacturing date code: Calendar year (last two digits)
WW
Manufacturing date code: Calendar week
14
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Chopper Stabilization Technique
Chopper Stabilization is an innovative circuit technique that is used to minimize the offset voltage of a Hall
element and an associated on-chip amplifier. Allegro patented a Chopper Stabilization 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 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.
Regulator
Hall Element
Amp
Sample and
Hold
Clock/Logic
Low-Pass
Filter
Concept of Chopper Stabilization Technique
15
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Applications Information
Transient Common-Mode Voltage Rejection in the ACS706
In order to quantify transient common-mode voltage rejection for the ACS706, a device was soldered onto a printed
circuit board. A 0.1 μF bypass capacitor and a 5 V dc power supply were connected between VCC and GND (pins 8 and
5) for this device. A 10 kΩ load resistor and a 0.01 μF capacitor were connected in parallel between the VOUT pin and
the GND pin of the device (pins 7 and 5).
1
8
2
7
I
P
3
4
V1
VOUT=0V
VOUT=20VPP
freq=variable
6
Vcc
Output
C0
C=0.1µF
V0
VDC=5V
C3
C=0.01µF
R=10kΩ
R0
5
Ground
GND
ACS706 Schematic Diagram of the Circuit used to Measure Transient Rejection
A function generator was connected between the primary current conductor (pins 1 thru 4) and the GND pin of
the device (pin 5). This function generator was configured to generate a 10 V peak (20 V peak-to-peak) sine
wave between pins 1-4 and pin 5. Note that the sinusoidal stimulus was applied such that no electrical current
would flow through the copper conductor composed of pins 1-4 of this device.
The frequency of this sine wave was varied from 60 Hz to 5 MHz in discrete steps. At each frequency, the
statistics feature of an oscilloscope was used to measure the voltage variations (noise) on the ACS706 output
in mV (peak to peak). The noise was measured both before and after the application of the stimulus. Transient
common-mode voltage rejection as a function of frequency is shown in the following figure.
Transient Rejection (dB)
–30
–35
–40
–45
–50
–55
–60
0.06
1
10
100
300
600
800
1000 3000 5000
Frequency of 20 V Peak-to-Peak Stimulus (kHz)
16
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
The Effect of PCB Layout on ACS706 Thermal Performance
Eight different PC boards were fabricated to characterize the effect of PCB design on the operating junction temperature of the
Hall-effect IC inside of the ACS706. These PC boards are shown in the figure below.
2 oz. Cu on one side of board
2 oz. Cu on both sides of board
An ACS706 device was soldered on to each PCB for thermal testing. The results of the testing are shown in the following table.
Test Results on Eight Thermal Characterization PCBs
Tested at 15A, TA = 20°C, still air, 2 oz. copper traces, current carried on and off board
by 14 gauge wires
PC Boards
Sides with Traces
1
2
Trace Width (mm)
Trace Length (mm)
Temperature Rise
Above Ambient (°C)
4
50
90
1.5
50
Overheated
4
10
48
1.5
10
110
4
50
53
1.5
50
106
4
10
38
1.5
10
54
17
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Improved PC Board Designs
The eight PC boards in the figure above do not represent an ideal PC board for use with the ACS706. The ACS706 evaluation
boards, for sale at the Allegro Web site On-Line Store, represent a more optimal PC board design (see photo below). On the
evaluation boards, the current to be sensed flows through very wide traces that were fabricated using 2 layers of 2 oz. copper.
Thermal management tests were conducted on the Allegro evaluation boards and all tests were performed using the same test
conditions described in the bulleted list above. The results for these thermal tests are shown in the table below. When using
the Allegro evaluation boards we see that even at an applied current of 20 A the junction temperature of the ACS706 is only
≈30 degrees above ambient temperature.
Test Results on Eight Electrical Characterization PCBs
Tested at TA = 20°C, still air
Applied Current
(A)
Temp Rise Above Ambient
(°C)
15
22
20
31
Allegro Current sensor evaluatin board with ACS706
and external connections.
18
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ACS706ELC-20A
Package LC, 8-pin SOIC
6.20 .244
5.80 .228
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
(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
4.00 .157
3.80 .150
1.27 .050
0.40 .016
A
A Terminal #1 mark area
1
2
0.25 .010
8X
SEATING
PLANE
0.10 [.004] C
8X
0.51 .020
0.31 .012
C
SEATING PLANE
GAUGE PLANE
1.75 .069
1.35 .053
0.25 [.010] M C A B
1.27 .050
0.25 .010
0.10 .004
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; 5,389,889;
5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents pending.
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, or manufacturability of its products. Before placing an order, the user is cautioned to verify that
the information being relied upon is current.
Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval.
The information included herein is believed to 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.
Copyright©2005, Allegro MicroSystems, Inc.
19
ACS706ELC20A-DS, Rev. 2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com