ACS709
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
Features and Benefits
Description
▪ Industry-leading noise performance with 120 kHz
bandwidth through proprietary amplifier and filter
design techniques
▪ Integrated shield greatly reduces capacitive coupling
from current conductor to die due to high dV/dt, and
prevents offset drift in high-side applications
▪ Small footprint surface mount QSOP24 package
▪ 2100 VRMS isolation voltage between primary current
path and sensor IC electronics
▪ 1.1 mΩ primary conductor resistance for low power loss
▪ User-settable Overcurrent Fault level
▪ Overcurrent Fault signal typically responds to an
overcurrent condition in < 2 μs
▪ Filter pin capacitor sets analog signal bandwidth
▪ ±2% typical output error
▪ 3 to 5.5 V, single supply operation
▪ Factory trimmed sensitivity, quiescent output voltage,
and associated temperature coefficients
▪ Chopper stabilization results in extremely stable
quiescent output voltage
▪ Ratiometric output from supply voltage
The Allegro® ACS709 current sensor IC provides economical
and precise means for current sensing applications in industrial,
automotive, commercial, and communications systems. The
device is offered in a small footprint surface mount package
that allows easy implementation in customer applications.
Package: 24 pin QSOP (suffix LF)
The ACS709 consists of a precision linear Hall sensor integrated
circuit with a copper conduction path located near the surface
of the silicon die. Applied current flows through the copper
conduction path, and the analog output voltage from the Hall
sensor IC linearly tracks the magnetic field generated by the
applied current. The accuracy of the ACS709 is maximized
with this patented packaging configuration because the Hall
element is situated in extremely close proximity to the current
to be measured.
High level immunity to current conductor dV/dt and stray
electric fields, offered by Allegro proprietary integrated shield
technology, guarantees low output ripple and low offset drift
in high-side applications.
The voltage on the Overcurrent Input (VOC pin) allows
customers to define an overcurrent fault threshold for the
device. When the current flowing through the copper conduction
path (between the IP+ and IP– pins) exceeds this threshold,
Continued on the next page…
Approximate Scale
Typical Application
1
2
3
4
5
6
IP
7
8
9
10
11
12
ACS709-DS
NC 24
IP+
NC 23
Fault_EN
22
IP+
IP+
IP+
IP+
FAULT_EN
ACS709
VOC
VCC
IP+
FAULT
IP–
VIOUT
IP–
FILTER
IP–
VZCR
IP–
GND
RH
VCC
RH, RL
21
330 kΩ
19
18
17
COC
IP–
NC 14
IP–
NC 13
0.1 μF
B
VIOUT
16
15
CF
RL
20
CF
1 nF
A
COC
Sets resistor divider reference for VOC
Noise and bandwidth limiting filter capacitor
Fault delay setting capacitor, 22 nF maximum
A
Use of capacitor required
B
Use of resistor optional
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
Description (continued)
the open drain Overcurrent Fault pin will transition to a logic low
state. Factory programming of the linear Hall sensor IC inside of
the ACS709 results in exceptional accuracy in both analog and
digital output signals.
The internal resistance of the copper path used for current sensing is
typically 1.1 mΩ, for low power loss. Also, the current conduction
path is electrically isolated from the low voltage device inputs and
outputs. This allows the ACS709 family of sensor ICs to be used
in applications requiring electrical isolation, without the use of
opto-isolators or other costly isolation techniques.
Applications include:
• Motor control and protection
• Load management and overcurrent detection
• Power conversion and battery monitoring / UPS systems
Selection Guide
IP(LIN)
(A)
Sens
(Typ at VCC = 5 V)
(mV/A)
ACS709LLFTR-35BB-T
75
28
ACS709LLFTR-20BB-T
37.5
56
Part Number
TA
(°C)
–40 to 150
Packing*
Tape and Reel, 2500 pieces per reel
*Contact Allegro for packing options.
Absolute Maximum Ratings
Characteristic
Rating
Units
VCC
8
V
Filter Pin
VFILTER
8
V
Analog Output Pin
VIOUT
32
V
VOC
8
V
Supply Voltage
Overcurrent Input Pin
¯¯A¯U¯¯L¯¯T
¯ Pin
Overcurrent ¯F
Symbol
Notes
V ¯F¯¯A¯U¯¯L¯¯T¯
8
V
Fault Enable (FAULT_EN) Pin
VFAULTEN
8
V
Voltage Reference Output Pin
VZCR
8
V
DC Reverse Voltage: Supply Voltage, Filter, Analog
Output, Overcurrent Input, Overcurrent Fault, Fault
Enable, and Voltage Reference Output Pins
VRdcx
–0.5
V
Isolation Voltage
VISO
2100
VAC
IIOUT(Source)
3
mA
IIOUT(Sink)
1
mA
–40 to 150
°C
Output Current Source
Output Current Sink
Operating Ambient Temperature
TA
60 Hz AC, TA = 25°C, 1 minute
Range L
Junction Temperature
TJ(max)
165
°C
Storage Temperature
Tstg
–65 to 170
°C
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
Functional Block Diagram
VCC
Hall
Bias
FAULT_EN
D
Q
CLK
R
POR
POR
FAULT Reset
Drain
–
VOC
+
2VREF
Control
Logic
FAULT
3 mA
Fault
Comparator
–
Sensitivity
Trim
IP+
VZCR
+
VIOUT
Signal
Recovery
RF(INT)
Hall
Amplifier
IP–
VOUT(Q)
Trim
GND
FILTER
Terminal List Table
Number
Pin-out Diagram
Name
Description
1 through 6
IP+
Sensed current copper conduction path pins. Terminals for current being sensed;
fused internally, loop to IP– pins; unidirectional or bidirectional current flow.
7 through 12
IP–
Sensed current copper conduction path pins. Terminals for current being sensed;
fused internally, loop to IP+ pins; unidirectional or bidirectional current flow.
No connection
IP+ 1
24 NC
13, 14, 23, 24
NC
IP+ 2
23 NC
15
GND
Device ground connection.
IP+ 3
22 FAULT_EN
IP+ 4
21 VOC
16
VZCR
IP+ 5
20 VCC
Voltage Reference Output pin. Zero current (0 A) reference; output voltage on this
pin scales with VCC .
IP+ 6
19 FAULT
17
FILTER
Filter pin. Terminal for an external capacitor connected from this pin to GND to set
the device bandwidth.
IP– 7
18 VIOUT
IP– 8
17 FILTER
18
VIOUT
IP– 9
16 VZCR
Analog Output pin. Output voltage on this pin is proportional to current flowing
through the loop between the IP+ pins and IP– pins.
IP– 10
15 GND
19
¯F
¯¯A¯U¯¯L¯¯T
¯
IP– 11
14 NC
Overcurrent Fault pin. When current flowing between IP+ pins and IP– pins
exceeds the overcurrent fault threshold, this pin transitions to a logic low state.
IP– 12
13 NC
20
VCC
Supply voltage.
21
VOC
Overcurrent Input pin. Analog input voltage on this pin sets the overcurrent fault
threshold.
22
¯¯A¯U¯¯L¯¯T
¯ when low.
FAULT_EN Enables overcurrent faulting when high. Resets ¯F
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
ACS709
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
COMMON OPERATING CHARACTERISTICS Valid at TA = –40°C to 150°C, VCC = 5 V, unless otherwise specified
Characteristic
ELECTRICAL CHARACTERISTICS
Supply Voltage1
Nominal Supply Voltage
Supply Current
Output Capacitance Load
Output Resistive Load
Magnetic Coupling from Device Conductor
to Hall Element
Internal Filter Resistance2
Symbol
Min.
Typ.
Max.
Units
3
–
–
5
5.5
–
V
V
¯¯A¯U¯¯L¯¯T
¯ pin high
VIOUT open, ¯F
VIOUT pin to GND
VIOUT pin to GND
–
–
10
11
–
–
14.5
10
–
mA
nF
kΩ
Current flowing from IP+ to IP– pins
–
9.5
–
G/A
–
1.7
–
kΩ
–
1.1
–
mΩ
–0.75
99.1
–
±0.25
100
VCC×0.5
0.75
100.9
–
%
%
V
–
3
–
μs
–
1
–
μs
–
4
–
μs
–
120
–
kHz
–
35
–
μs
VOC
VCC×0.25
–
VCC×0.4
V
INCOMP
–
±1
–
A
Switchpoint in VOC safe operating area;
assumes INCOMP = 0 A
–
±5
–
%
¯¯A¯U¯¯L¯¯T
¯ pin
1 mA sink current at ¯F
–
–
0.4
V
VCC
VCCN
ICC
CLOAD
RLOAD
MCHALL
RF(INT)
Primary Conductor Resistance
RPRIMARY
ANALOG OUTPUT SIGNAL CHARACTERISTICS
Full Range Linearity3
ELIN
Symmetry4
ESYM
Bidirectional Quiescent Output
VOUT(QBI)
TIMING PERFORMANCE CHARACTERISTICS
VIOUT Signal Rise Time
VIOUT Signal Propagation Time
VIOUT Signal Response Time
tr
tPROP
tRESPONSE
VIOUT Large Signal Bandwidth5
f3dB
Power-On Time
tPO
OVERCURRENT CHARACTERISTICS
Setting Voltage for Overcurrent Switchpoint6
Signal Noise at Overcurrent
Comparator Input
Test Conditions
Overcurrent Fault Switchpoint Error7,8
EOC
¯¯A¯U¯¯L¯¯T
¯ Pin Output Voltage
Overcurrent ¯F
V ¯F¯¯A¯U¯¯L¯¯T¯
TA = 25°C
IP = ±IP0A
IP = ±IP0A
IP = 0 A, TA = 25°C
TA = 25°C, Swing IP from 0 A to IP0A,
no capacitor on FILTER pin, 100 pF from
VIOUT to GND
TA = 25°C, no capacitor on FILTER pin,
100 pF from VIOUT to GND
TA = 25°C, Swing IP from 0 A to IP0A,
no capacitor on FILTER pin, 100 pF from
VIOUT to GND
–3 dB, TA = 25°C, no capacitor on FILTER
pin, 100 pF from VIOUT to GND
Output reaches 90% of steady-state level,
no capacitor on FILTER pin, TA = 25°C
Fault Enable (FAULT_EN Pin) Input Low
Voltage Threshold
VIL
–
–
0.1 × VCC
V
Fault Enable (FAULT_EN Pin) Input High
Voltage Threshold
VIH
0.8 × VCC
–
–
V
Fault Enable (FAULT_EN Pin) Input
Resistance
RFEI
–
1
–
MΩ
Continued on the next page…
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
ACS709
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
COMMON OPERATING CHARACTERISTICS (continued) Valid at TA = –40°C to 150°C, VCC = 5 V, unless otherwise specified
Characteristic
Symbol
OVERCURRENT CHARACTERISTICS (continued)
Overcurrent Fault Response Time
tOC
Overcurrent Fault Reset Delay
tOCR
Overcurrent Fault Reset Hold Time
tOCH
Overcurrent Input Pin Resistance
VOLTAGE REFERENCE CHARACTERISTICS
Voltage Reference Output
ROC
VZCR
Test Conditions
Switchpoint set at 90% of IPOA,
delay from IP exceeding overcurrent
fault threshold to V ¯F¯¯A¯U¯¯L¯¯T¯ < 0.4 V, without
external COC capacitor
Time from VFAULTEN < VIL to
VFAULT > 0.8 × VCC , RPU = 330 kΩ
Time from VFAULTEN pin < VIL to reset of
fault latch; see Functional Block Diagram
TA = 25°C, VOC pin to GND
Min.
Typ.
Max.
Units
–
1.9
–
μs
–
500
–
ns
–
250
–
ns
2
–
–
MΩ
TA = 25 °C
Source current
Sink current
–
0.5 × VCC
–
V
3
–
–
mA
Voltage Reference Output Load Current
IZCR
50
–
–
μA
Voltage Reference Output Drift
∆VZCR
–
±10
–
mV
1Devices are trimmed for maximum accuracy at V
CC = 5 V. The ratiometry feature of the device allows operation over the full VCC range; however, accuracy
may be slightly degraded for VCC values other than 5 V. Contact the Allegro factory for applications that require maximum accuracy for VCC = 3.3 V.
2R
F(INT) forms an RC circuit via the FILTER pin.
3This parameter can drift by as much as 0.25% over the lifetime of this product.
4This parameter can drift by as much as 0.3% over the lifetime of this product.
5Calculated using the formula f
3dB = 0.35 / tr .
6See page 8 on how to set overcurrent fault switchpoint.
7Switchpoint can be lower at the expense of switchpoint accuracy.
8This error specification does not include the effect of noise. See the I
NCOMP specification in order to factor in the additional influence of noise on the
fault switchpoint.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
X20B PERFORMANCE CHARACTERISTICS, TA Range L, valid at TA = – 40°C to 150°C, VCC = 5 V, unless otherwise specified
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Optimized Accuracy Range
IP(OA)
–20
–
20
A
Linear Sensing Range
IP(LIN)
–37.5
–
37.5
A
–
1.50
–
mV
Performance Characteristics at VCC = 5 V
Noise1
VNOISE(rms) TA = 25°C, Sens = 56 mV/A, Cf = 0, CLOAD = 4.7 nF, RLOAD open
IP = 12.5 A, TA = 25°C
Sensitivity2,3
Sens
–
56
–
mV/A
IP = 12.5 A, TA = 25°C to 150°C
54.5
–
58
mV/A
IP = 12.5 A, TA = – 40°C to 25°C
54.5
–
58.5
mV/A
–
±5
–
mV
IP = 0 A, TA = 25°C to 150°C
–25
–
25
mV
IP = 0 A, TA = – 40°C to 25°C
–40
–
40
mV
Tested at IP =12.5 A, IP applied for 5 ms, TA = 25°C to 150°C
–
±2
–
%
Tested at IP =12.5 A, IP applied for 5 ms, TA = – 40°C to 25°C
–
±3
–
%
IP = 0 A, TA = 25°C
Electrical Offset
Voltage2
Total Output Error2,4
VOE
ETOT
1V
pk-pk noise (6 sigma noise) is equal to 6 × VNOISE(rms). Lower noise levels than this can be achieved by using Cf for applications requiring narrower
bandwidth. See Characteristic Performance page for graphs of noise versus Cf and bandwidth versus Cf.
2See Characteristic Performance Data graphs for parameter distribution over ambient temperature range.
3This parameter can drift by as much as 1.75% over lifetime of the product.
4This parameter can drift by as much as 2.5% over lifetime of the product.
X35B PERFORMANCE CHARACTERISTICS, TA Range L, valid at TA = – 40°C to 150°C, VCC = 5 V, unless otherwise specified
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Optimized Accuracy Range
IP(OA)
–37.5
–
37.5
A
Linear Sensing Range
IP(LIN)
–75
–
75
A
–
1
–
mV
mV/A
Performance Characteristics at VCC = 5 V
Noise1
VNOISE(rms) TA = 25°C, Sens = 28 mV/A, Cf = 0, CLOAD = 4.7 nF, RLOAD open
IP = 25 A, TA = 25°C
Sensitivity2,3
Sens
–
28
–
IP = 25 A, TA = 25°C to 150°C
27
–
29.5
mV/A
IP = 25 A, TA = – 40°C to 25°C
27
–
29.5
mV/A
IP = 0 A, TA = 25°C
Electrical Offset Voltage2
Total Output Error2,4
VOE
ETOT
–
±5
–
mV
IP = 0 A, TA = 25°C to 150°C
–25
–
25
mV
IP = 0 A, TA = – 40°C to 25°C
–40
–
40
mV
Tested at IP = 25 A, IP applied for 5 ms, TA = 25°C to 150°C
–
±3
–
%
Tested at IP = 25 A, IP applied for 5 ms, TA = – 40°C to 25°C
–
±3
–
%
1V
pk-pk
noise (6 sigma noise) is equal to 6 × VNOISE(rms). Lower noise levels than this can be achieved by using Cf for applications requiring narrower
bandwidth. See Characteristic Performance page for graphs of noise versus Cf and bandwidth versus Cf.
2See Characteristic Performance Data graphs for parameter distribution over ambient temperature range.
3This parameter can drift by as much as 1.75% over lifetime of the product.
4This parameter can drift by as much as 2.5% over lifetime of the product.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
ACS709
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
Thermal Characteristics
Characteristic
Symbol
Steady State Package Thermal Resistance
Transient Package Thermal Resistance
Test Conditions
Value
Units
RθJA
Tested with 30 A DC current and based on ACS709 demo
board in 1 cu. ft. of still air. Please refer to product FAQs
page on Allegro web site for detailed information on
ACS709 demo board.
21
ºC/W
RTθJA
Tested with 30 A DC current and based on ACS709 demo
board in 1 cu. ft. of still air. Please refer to product FAQs
page on Allegro web site for detailed information on
ACS709 demo board.
See graph
ºC/W
ACS709 Transient Package Thermal Resistance
On 85--0444 Demo Board (No Al Plate)
22
20
Thermal Resistance (°C/W)
18
16
14
12
10
8
6
4
2
0
0.01
0.1
1
10
100
1000
Time (Sec)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
Characteristic Performance
ACS709 Bandwidth versus External Capacitor Value, CF
Capacitor connected between FILTER pin and GND
1000
Bandwidth (kHz)
100
10
1
0.1
0.01
0.1
1
10
100
1000
Capacitance (nF)
ACS709 Noise versus External Capacitor Value, CF
Capacitor connected between FILTER pin and GND
ACS709x-35B
V CC = 3.3 V
1000
900
900
800
RMS Noise (μV)
RMS Noise (μV)
ACS709x-35B
V CC = 5 V
800
700
600
700
600
500
400
500
300
400
0
10
20
30
40
0
50
10
Capacitance (nF)
ACS709x-20B
V CC = 5 V
30
40
50
40
50
ACS709x-20B
V CC = 3.3 V
1600
1400
1400
1200
1200
RMS Noise (μV)
RMS Noise (μV)
1600
20
Capacitance (nF)
1000
800
600
400
200
1000
800
600
400
200
0
0
0
10
20
30
Capacitance (nF)
40
50
0
10
20
30
Capacitance (nF)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
Characteristic Performance Data
Data taken using the ACS709-20BB, VCC = 5 V
Accuracy Data
20
15
10
5
0
-5
-10
-15
-20
-25
-30
-35
–50
Sensitivity versus Ambient Temperature
58.0
57.5
Sens (mV/A)
VOE (mV)
Electrical Offset Voltage versus Ambient Temperature
57.0
56.5
56.0
55.5
-25
0
25
50
75
100
125
55.0
–50
150
-25
0
25
TA (°C)
75
100
125
150
TA (°C)
Nonlinearity versus Ambient Temperature
Symmetry versus Ambient Temperature
0.20
100.8
0.15
100.6
0.10
100.4
ESYM (%)
0.05
0
-0.05
-0.10
-0.15
100.2
100.0
99.8
-0.20
99.6
-0.25
-0.30
–50
99.4
-25
0
25
50
75
100
125
–50
150
-25
0
25
TA (°C)
50
75
100
125
150
TA (°C)
Total Output Error versus Ambient Temperature
4
3
2
1
ETOT (%)
ELIN (%)
50
0
-1
-2
-3
-4
–50
-25
0
25
50
75
100
125
150
TA (°C)
Typical Maximum Limit
Mean
Typical Minimum Limit
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
Characteristic Performance Data
Data taken using the ACS709-35BB, VCC = 5 V
Accuracy Data
Sensitivity versus Ambient Temperature
20
29.0
15
28.8
10
28.6
Sens (mV/A)
VOE (mV)
Electrical Offset Voltage versus Ambient Temperature
5
0
-5
-10
28.4
28.2
28.0
-15
27.8
-20
27.6
-25
–50
-25
0
25
50
75
100
125
27.4
–50
150
-25
0
25
TA (°C)
75
100
125
150
TA (°C)
Nonlinearity versus Ambient Temperature
Symmetry versus Ambient Temperature
0.30
101.0
100.8
0.20
100.6
ESYM (%)
0.10
0
-0.10
100.4
100.2
100.0
99.8
99.6
99.4
-0.20
99.2
-0.30
–50
-25
0
25
50
75
100
125
99.0
–50
150
-25
0
25
TA (°C)
50
75
100
125
150
TA (°C)
Total Output Error versus Ambient Temperature
4
3
2
1
ETOT (%)
ELIN (%)
50
0
-1
-2
-3
-4
–50
-25
0
25
50
75
100
125
150
TA (°C)
Typical Maximum Limit
Mean
Typical Minimum Limit
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
Setting Overcurrent Fault Switchpoint
The VOC needed for setting the overcurrent fault
switchpoint can be calculated as follows:
VOC = Sens × | IOC | ,
where VOC is in mV, Sens in mV/A, and IOC (overcurrent fault switchpoint) in A.
| Ioc | is the overcurrent fault switchpoint for a bidirectional (AC) current, which means a bi-directional
device will have two symmetrical overcurrent fault
switchpoints, +IOC and –IOC .
See the following graph for IOC and VOC ranges.
IOC versus VOC
IOC
0.4 VCC / Sens
Not in Valid Range
In Valid Range
0.25 VCC / Sens
0
0. 25 VCC
0. 4 VCC
VOC
– 0.25 VCC / Sens
– 0.4 VCC / Sens
Example: For ACS709LLFTR-35BB-T, if required overcurrent fault switchpoint is 50 A, and VCC = 5 V, then the
required VOC can be calculated as follows:
VOC = Sens × IOC = 28 × 50 = 1400 (mV)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
Functional Description
Overcurrent Fault Operation
The primary concern with high-speed fault detection is that noise
may cause false tripping. Various applications have or need to
be able to ignore certain faults that are due to switching noise
or other parasitic phenomena, which are application dependant.
The problem with simply trying to filter out this noise up front is
that in high-speed applications, with asymmetric noise, the act of
filtering introduces an error into the measurement. To get around
this issue, and allow the user to prevent the fault signal from
¯¯T
¯
being latched by noise, a circuit was designed to slew the ¯F¯A¯¯U¯¯L
pin voltage based on the value of the capacitor from that pin to
ground. Once the voltage on the pin falls below 2 V, as established by an internal reference, the fault output is latched and
pulled to ground quickly with an internal N-channel MOSFET.
Fault Walk-through
The following walk-through references various sections and
attributes in the figure below. This figure shows different
fault set/reset scenarios and how they relate to the voltages on
¯¯T
¯ pin, FAULT_EN pin, and the internal Overcurrent
the ¯F¯A¯¯U¯¯L
(OC) Fault node, which is invisible to the customer.
1.Because the device is enabled (FAULT_EN is high) and there is
¯¯T
¯ pin starts discharging.
an OC fault condition, the device ¯F¯A¯¯U¯¯L
VCC
1
¯¯T
¯ pin voltage reaches approximately 2 V, the
2. When the ¯F¯A¯¯U¯¯L
¯¯T
¯
fault is latched, and an internal NMOS device pulls the ¯F¯A¯¯U¯¯L
¯¯T
¯
pin voltage to approximately 0 V. The rate at which the ¯F¯A¯¯U¯¯L
pin slews downward (see [4] in the figure) is dependent on the
¯¯T
¯ pin.
external capacitor, COC, on the ¯F¯A¯¯U¯¯L
¯¯T
¯ pin starts
3.When the FAULT_EN pin is brought low, the ¯F¯
A¯¯U¯¯L
resetting if no OC Fault condition exists. The internal NMOS
pull-down turns off and an internal PMOS pull-up turns on (see
[7] if the OC Fault condition still exists).
4. The slope, and thus the delay, on the fault is controlled by the
¯¯T
¯ pin to ground. During this
capacitor, COC, placed on the ¯F¯A¯¯U¯¯L
¯¯T
¯ pin is between VCC and
portion of the fault (when the ¯F¯A¯¯U¯¯L
2 V), there is a 3 mA constant current sink, which discharges
COC. The length of the fault delay, t, is equal to:
t=
(1)
where VCC is the device power supply voltage.
¯¯T
¯ pin did not reach the 2 V latch point before
5. The ¯F¯A¯¯U¯¯L
the OC fault condition cleared. Because of this, the fixed 3 mA
current sink turns off, and the internal PMOS pull-up turns on to
¯¯T
¯ pin.
recharge COC through the ¯F¯A¯¯U¯¯L
1
1
6
4
4
8
4
FAULT
(Output)
2V
COC ( VCC – 2 V )
3 mA
6
5
2
4
2
6
2
7
3
0V
Time
FAULT_EN
(Input)
OC Fault
Condition
(Active High)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
6.
This curve shows VCC charging external capacitor COC
through the internal PMOS pull-up. The slope is determined
by COC.
7.
When the FAULT_EN pin is brought low, if the fault condi¯¯T
¯ pin will stay low until
tion still exists, the latched ¯F¯A¯¯U¯¯L
the fault condition is removed, then it will start resetting.
8.
At this point there is a fault condition, and the part is enabled
¯¯T
¯ pin can charge to VCC. This shortens the
before the ¯F¯A¯¯U¯¯L
user-set delay, so the fault is latched earlier. The new delay
time can be calculated by equation 1, after substituting the
¯¯T
¯ pin for VCC.
voltage seen on the ¯F¯A¯¯U¯¯L
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
Clock/Logic
Amp
Sample and
Hold
Hall Element
Low-Pass
Filter
Concept of Chopper Stabilization Technique
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
13
ACS709
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
Definitions of Accuracy Characteristics
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 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 device 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–
VIOUT_full-scale amperes – VIOUT(Q)
2 (VIOUT_1/2 full-scale amperes – VIOUT(Q) )
[{
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 fullscale 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 (%).
100
VCC / 5 V
The ratiometric change in sensitivity, SensRAT (%), is defined as:
where VIOUT_full-scale amperes = the output voltage (V) when the
sensed current approximates full-scale ±IP .
100
Symmetry (ESYM). The degree to which the absolute voltage
output from the device varies in proportion to either a positive
or negative full-scale primary current. The following formula is
used to derive symmetry:
100
VIOUT(Q)VCC / VIOUT(Q)5V
SensVCC / Sens5V
VCC / 5 V
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)
VIOUT(Q) – VIOUT_–full-scale amperes
Accuracy
25°C Only
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 0.5×VCC. For example, in the case of a
bidirectional output device, 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 output from its ideal quiescent voltage 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 at right. Note that error is
directly measured during final test at Allegro.
Average
VIOUT
Accuracy
Over $Temp erature
Accuracy
25°C Only
IP(min)
–IP (A)
+IP (A)
Full Scale
IP(max)
0A
Accuracy
25°C Only
Accuracy
Over $Temp erature
Decreasing VIOUT(V)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
14
ACS709
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
Definitions of Dynamic Response Characteristics
I (%)
Propagation delay (tPROP). The time required for the device
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.
Primary Current
90
Transducer Output
0
Propagation Time, tPROP
I (%)
Response time (tRESPONSE). The time interval between a) when
the primary current signal reaches 90% of its final value, and b)
when the device reaches 90% of its output corresponding to the
applied current.
t
Primary Current
90
Transducer Output
0
Response Time, tRESPONSE
I (%)
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 current sensor IC, 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.
t
Primary Current
90
Transducer Output
10
0
Rise Time, tr
t
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
15
High Bandwidth, Fast Fault Response Current Sensor IC
In Thermally Enhanced Package
ACS709
Package LF, 24-pin QSOP
8º
0º
8.66 ±0.10
24
0.25
0.15
3.91 ±0.10
2.30
5.00
5.99 ±0.20
A
1.27
0.41
1
1.04 REF
2
0.25 BSC
Branded Face
24X
1.75 MAX
0.20 C
0.30
0.20
0.635 BSC
SEATING
PLANE
C
0.40
0.635
B
SEATING PLANE
GAUGE PLANE
0.25 MAX
PCB Layout Reference View
NNNNNNNNNNNNN
TLF-AAA
For Reference Only, not for tooling use (reference JEDEC MO-137 AE)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
LLLLLLLLLLL
A Terminal #1 mark area
B Reference pad layout (reference IPC7351 SOP63P600X175-24M)
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances
C Branding scale and appearance at supplier discretion
C
Standard Branding Reference View
N = Device part number
T = Temperature code
LF = (Literal) Package type
A = Amperage
Copyright ©2008-2009, Allegro MicroSystems, Inc.
The products described herein are protected by U.S. patents: 7,166,807; 7,425,821; 7,573,393; and 7,598,601.
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’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 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.
For the latest version of this document, visit our website:
www.allegromicro.com
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
16