Data Sheet
ACHS-7121/7122/7123
Fully Integrated, Hall Effect-Based Linear
Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
Overview
Features
The Broadcom® ACHS-7121/7122/7123 product series is a
fully integrated Hall Effect-based isolated linear current sensor
device family designed for AC or DC current sensing in
industrial, commercial, and communications systems. Each of
the ACHS-7121/7122/7123 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 that 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 CMOS Hall IC, which is programmed for
accuracy after packaging. The output of the device has a
positive slope (>VOUT(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 0.7 mΩ
typical, providing low-power loss. The terminals of the
conductive path are electrically isolated from the signal leads
(pins 5 through 8). This performance is delivered in a compact,
surface mountable, SO-8 package that meets worldwide
regulatory safety standards.
Wide Operating Temperature: –40ºC to 110ºC
Primary conductor resistance: 0.7 mΩ typ.
Sensing current range: ±10A, ±20A, and ±30A
Output sensitivity: 66 to 185 mV/A
Output voltage proportional to AC or DC currents
Ratiometric output from supply voltage
Single supply operation: 5.0V
Low-noise analog signal path
Device bandwidth is set via FILTER pin:
80 kHz typ. Bandwidth with 1 nF filter capacitor
Factory-trimmed for accuracy
Extremely stable output offset voltage
Near zero magnetic hysteresis
Typical total output error of ±1.5%
>25 kV/μs Common-Mode Transient Immunity
Small footprint, low-profile SO-8 package
Worldwide Safety Approval: UL, CSA:
Isolation Voltage 3 kVRMS, 1 minute
Applications
Part Number
Current Range
Sensitivity
ACHS-7121
±10A
185 mV/A
ACHS-7122
±20A
100 mV/A
ACHS-7123
±30A
66 mV/A
Low-power inverter current sensing
Motor phase and rail current sensing
Solar inverters
Chargers and Converters
Switching Power Supplies
CAUTION! It is advised that normal static precautions be taken in handling and assembly of this component to prevent
damage and/or degradation which may be induced by ESD. The components featured in this data sheet are not
to be used in military or aerospace applications or environments.
Broadcom
ACHS-712x-DS101
February 28, 2018
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Functional Diagram
I P+
1
8
VDD
I P+
I P–
I P–
2
7
3
6
4
5
VOUT
FILTER
GND
NOTE:
The connection of 1 μF bypass capacitor between pins 8 and 5 is recommended.
Pin Description
Pin
Pin Name
Description
Pin
Pin Name
Description
1
IP+
8
VDD
Supply voltage relative to GND
2
IP+
Terminals for current being sampled; fused
internally
7
VOUT
Output Voltage
3
IP–
6
FILTER
Filter pin to set bandwidth
4
IP–
Terminals for current being sampled; fused
internally
5
GND
Output side ground
Typical Application Circuit
A typical application circuit for the ACHS-7121/7122/7123 product series consists of a bypass capacitor and a filter capacitor
as additional external components. On the input side, pins 1 and 2 are shorted together and pins 3 and 4 shorted together.
The output voltage is directly measured from the VOUT pin.
5V
I P+
I P–
Broadcom
I P+
VDD
I P+
I P–
I P–
VOUT
FILTER
GND
CBYPASS
OUTPUT
CF
ACHS-712x-DS101
2
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Ordering Information
Option
Part Number
ACHS-7121
ACHS-7122
ACHS-7123
UL 3 kVRMS
Current Range
(RoHS)
Compliant
Package
Surface Mount
±10A
-000E
SO-8
X
±20A
±30A
-500E
X
-000E
X
-500E
X
-000E
X
-500E
X
Tape and Reel
X
X
X
1 min. rating
Quantity
X
100 per tube
X
1500 per reel
X
100 per tube
X
1500 per reel
X
100 per tube
X
1500 per reel
To order, choose a part number from the part number column and combine with the desired option from the option column
to form an order entry.
Example: Select ACHS-7122-500E to order product of ±20A, surface-mount package in tape and reel packaging and
RoHS compliance. Contact your Broadcom sales representative or authorized distributor for information.
Option data sheets are available. Contact your Broadcom sales representative or authorized distributor for information.
Broadcom
ACHS-712x-DS101
3
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Package Outline Drawing
ACHS-7121/7122/7123 SO-8 Package
1.27
(0.050)
0.457
(0.018)
8
7
6
5
Part Number
XXXX
YYWW
EEE
Datecode
RoHS
Compliance
7.49
(0.295)
+0.254
3.937 –0.127
(0.155 +0.010
)
–0.005
Lot ID
1.9 (0.075)
1
2
3
4
0.64 (0.025)
+0.254
5.080 –0.127
(0.200 +0.010
)
–0.005
7°
0.254 ±0.050
(0.010 ±0.002)
1.908 ±0.127
(0.075 ±0.005)
0.381±0.127
(0.015 ±0.005)
0.800 ±0.127
(0.031 ±0.005)
0.203 ±0.100
(0.008 ±0.004)
0° to 7°
+0.254
6.000 –0.127
+0.010
(0.236 –0.005)
Dimensions in millimeters (inches).
NOTE:
Lead Coplanarity = 0.100 mm (0.004 inches) max.
Floating lead protrusion = 0.254 mm (0.010 inches) max.
Mold Flash on each side = 0.127 mm (0.005 inches) max.
Recommended Pb-Free IR Profile
Recommended reflow condition as per JEDEC Standard, J-STD-020 (latest revision). Non-halide flux should be used.
Broadcom
ACHS-712x-DS101
4
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Regulatory Information
The ACHS-7121/7122/7123 is approved by the following organizations:
UL/cUL
UL 1577, component recognition program up to VISO = 3000VRMS. Approved under CSA Component Acceptance Notice #5.
Insulation and Safety Related Specifications
Parameter
Symbol
Value
Unit
Conditions
Minimum External Air Gap (External
Clearance)
L(101)
4.0
mm
Measured from input terminals to output terminals,
shortest distance through air.
Minimum External Tracking (External
Creepage)
L(102)
4.0
mm
Measured from input terminals to output terminals,
shortest distance path along body.
—
0.05
mm
Through insulation distance, conductor to conductor,
usually the direct distance between the primary input
conductor and detector IC.
Tracking Resistance (Comparative
Tracking Index)
CTI
>175
V
DIN IEC 112/VDE 0303 Part 1.
Isolation Group
—
IIIa
—
Material Group (DIN VDE 0110, 1/89, Table 1).
Minimum Internal Plastic Gap (Internal
Clearance)
Absolute Maximum Rating
Parameter
Symbol
Min.
Max.
Unit
Storage Temperature
TS
–55
125
°C
—
Ambient Operating Temperature
TA
–40
110
°C
—
Junction Temperature
TJ
—
150
°C
—
Primary Conductor Lead Temperature
TL
—
150
°C
Pins 1, 2, 3, or 4
Supply Voltages
VDD
–0.5
8.0
V
—
Output Voltage
VOUT
–0.5
VDD + 0.5
V
—
IOUT(source)
—
10
mA
TA = 25°C
IOUT(sink)
—
10
mA
TA = 25°C
IP
—
100
A
PIN
—
900
mW
TA = 25°C
POUT
—
90
mW
TA = 25°C
Output Current Source
Output Current Sink
Overcurrent Transient Tolerance
Input Power Dissipation
Output Power Dissipation
Broadcom
Test Conditions
1 pulse, 100 ms;
TA = 25°C
ACHS-712x-DS101
5
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Recommended Operating Conditions
Parameter
Symbol
Min.
Max.
Unit
TA
–40
110
°C
VDD
4.5
5.5
V
Output Capacitive Load
CLOAD
—
10
nF
Output Resistive Load
RLOAD
4.7
—
kΩ
IP
–10
10
A
ACHS-7122
–20
20
A
ACHS-7123
–30
30
A
Ambient Operating Temperature
Supply Voltage
Input Current Range
ACHS-7121
Common Electrical Specifications
Unless otherwise stated, all minimum/maximum specifications are over recommended operating conditions, CF = 1 nF.
All typical values are based on TA = 25°C, VDD = 5.0V, CF = 1 nF.
Parameter
Symbol
Min.
Typ.
Max.
Unit
Test Condition
Fig.
Note
IDD
—
13
15
mA
VDD = 5V, output
open
5,6
1
RPRIMARY
—
0.7
—
mΩ
—
—
1
Zero Current Output Voltage
VOUT(Q)
—
VDD/2
—
V
Bidirectional, IP=0A 2
1
Input Filter Resistance
RF(INT)
—
1.6
—
kΩ
—
—
1
Bandwidth
BW
—
80
—
kHz
–3 dB
—
1
Rise Time
tr
—
4
—
μs
—
10
1
tPO
—
21
—
μs
—
8
1
CMTI
25
—
—
kV/us
VCM = 1000V
—
3
Supply Current
Primary Conductor Resistance
Power-on Time
Common Mode Transient Immunity
Electrical Specifications
ACHS-7121
Unless otherwise stated, all minimum/maximum specifications are over recommended operating conditions, CF = 1 nF.
All typical values are based on TA = 25°C, VDD = 5.0V, CF = 1 nF.
Parameter
Optimized Input Current Range
Symbol
Min.
Typ.
Max.
Unit
IP
–10
—
10
A
Sensitivity
Sens
—
185
—
mV/A
Sensitivity Error
ESENS
–3
—
3
Sensitivity Slope
ΔSens
—
–0.04
Sensitivity Slope
ΔSens
—
VOE
ΔVOE
Zero Current Output Error
Zero Current Output Error Slope
Broadcom
Test Conditions
Fig.
Note
—
7
4
–10A ≤ IP ≤ 10A
1
1
%
TA = 25°C, VDD = 5V
1
1
—
mV/A/°C
TA = –40°C to 25°C
1
1
0.01
—
mV/A/°C
TA = 25°C to 110°C
1
1
–30
—
30
mV
TA = 25°C
2
1
—
–0.03
—
mV/°C
TA = –40°C to 25°C
2
1
ACHS-712x-DS101
6
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Parameter
Symbol
Min.
Typ.
Max.
Unit
ΔVOE
—
0.06
—
mV/°C
Output Noise
VN(RMS)
—
7.8
—
Nonlinearity
NL
—
0.27
ETOT
—
ESENS_DRIFT
ETOT_DRIFT
Zero Current Output Error Slope
Total Output Error
Sensitivity Error Lifetime Drift
Total Output Error Lifetime Drift
Test Conditions
Fig.
Note
TA = 25°C to 110°C
2
1
mV
BW = 2 kHz
9
10
—
%
—
3
2
±1.5
—
%
—
4
5
—
±2
—
%
—
—
1
—
±2
—
%
—
—
1
ACHS-7122
Unless otherwise stated, all minimum/maximum specifications are over recommended operating conditions, CF = 1 nF.
All typical values are based on TA = 25°C, VDD = 5.0V, CF = 1 nF.
Parameter
Symbol
Min.
Typ.
Max.
Unit
IP
–20
—
20
A
Sensitivity
Sens
—
100
—
mV/A
Sensitivity Error
ESENS
–3
—
3
%
Optimized Input Current Range
Test Conditions
Fig.
Note
—
7
4
–20A ≤ IP ≤ 20A
1
1
TA = 25°C, VDD = 5V
1
1
Sensitivity Slope
ΔSens
—
–0.01
—
mV/A/°C
TA = –40°C to 25°C
1
1
Sensitivity Slope
ΔSens
—
0.01
—
mV/A/°C
TA = 25°C to 110°C
1
1
VOE
–25
—
25
mV
TA = 25°C
2
1
Zero Current Output Error Slope
ΔVOE
—
0.01
—
mV/°C
TA = –40°C to 25°C
2
1
Zero Current Output Error Slope
ΔVOE
—
0.02
—
mV/°C
TA = 25°C to 110°C
2
1
Output Noise
VN(RMS)
—
4.1
—
mV
BW = 2 kHz
9
10
Nonlinearity
NL
—
0.18
—
%
—
3
2
Zero Current Output Error
Total Output Error
Sensitivity Error Lifetime Drift
Total Output Error Lifetime Drift
ETOT
—
±1.5
—
%
—
4
5
ESENS_DRIFT
—
±2
—
%
—
—
1
ETOT_DRIFT
—
±2
—
%
—
—
1
ACHS-7123
Unless otherwise stated, all minimum/maximum specifications are over recommended operating conditions, CF = 1 nF.
All typical values are based on TA = 25°C, VDD = 5.0V, CF = 1 nF.
Parameter
Optimized Input Current Range
Symbol
Min.
Typ.
Max.
Unit
Test Conditions
Fig.
Note
—
7
4
–30A ≤ IP ≤ 30A
1
1
TA = 25°C, VDD = 5V 1
1
IP
–30
—
30
A
Sensitivity
Sens
—
66
—
mV/A
Sensitivity Error
ESENS
–3
—
3
%
Sensitivity Slope
ΔSens
—
–0.01
—
mV/A/°C
TA = –40°C to 25°C
1
1
Sensitivity Slope
ΔSens
—
0.01
—
mV/A/°C
TA = 25°C to 110°C
1
1
VOE
–20
—
20
mV
TA = 25°C
2
1
Zero Current Output Error Slope
ΔVOE
—
0.01
—
mV/°C
TA = –40°C to 25°C
2
1
Zero Current Output Error Slope
ΔVOE
—
0.02
—
mV/°C
TA = 25°C to 110°C
2
1
Zero Current Output Error
Broadcom
ACHS-712x-DS101
7
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Parameter
Symbol
Min.
Typ.
Max.
Unit
Test Conditions
Fig.
Note
Output Noise
VN(RMS)
—
2.7
—
mV
BW = 2 kHz
9
10
Nonlinearity
NL
—
0.11
—
%
—
3
2
ETOT
—
±1.5
—
%
—
4
5
ESENS_DRIFT
—
±2
—
%
—
—
1
ETOT_DRIFT
—
±2
—
%
—
—
1
Total Output Error
Sensitivity Error Lifetime Drift
Total Output Error Lifetime Drift
Package Characteristics
Parameter
Symbol
Min.
Typ.
Max.
Input-Output Momentary Withstand Voltage
VISO
3000
—
—
Resistance (Input-Output)
RI-O
—
Capacitance (Input-Output)
CI-O
—
Junction-to-Ambient Thermal Resistance
(due to Primary Conductor)
Rθ12
Junction-to-Ambient Thermal Resistance
(due to IC)
Rθ22
Unit
Test Condition
Note
VRMS RH < 50%, t = 1 min., TA = 25°C
6, 7, 8
—
Ω
VI-O = 500VDC
8
1.3
—
pF
f = 1 MHz
8
—
55
—
°C/W
Based on the Broadcom evaluation
board
9
—
27
—
°C/W
Based on the Broadcom evaluation
board
9
10
14
NOTE:
1. Refer to the Definition of Electrical Characteristics in the Application Section of the data sheet.
2. Nonlinearity is defined as half of the peak-to-peak output deviation from the best-fit line, expressed as a
percentage of the full-scale output voltage. See the Definition of Electrical Characteristics in the Application
Section of the data sheet for the complete definition and formula.
3. Common Mode Transient Immunity is tested by applying a fast rising/falling voltage pulse across pin 4 and
GND (pin 5). The output glitch observed is less than 0.2V from the average output voltage for less than 1 μs.
4. Device may be operated at higher primary current levels, IP, provided that the Maximum Junction Temperature,
TJ(MAX) is not exceeded.
5. Total output error in percentage is the difference between the measured output voltage at maximum input
current (IPMAX) and the ideal output voltage at IPMAX divided by the ideal output voltage at IPMAX. The Total
Output Error typical value is based on total output error measured at the point of product release.
6. In accordance with UL 1577, each device is proof tested by applying an insulation test voltage ≥3600VRMS for
1 second.
7. The Input-Output Momentary Withstand Voltage is a dielectric voltage rating that should not be interpreted as
an input-output continuous voltage rating.
8. This is a two-terminal measurement: pins 1 through 4 are shorted together and pins 5 through 8 are shorted
together.
9. The Broadcom evaluation board has 300 mm2 (total area including top and bottom copper) of 2 oz. copper
connected to pins 1 and 2 and pins 3 and 4. Refer to the application section for additional information on thermal
characterization.
10. Output Noise is the noise level of the ACHS-7121/7122/7123 expressed in root mean square (RMS) voltage.
Broadcom
ACHS-712x-DS101
8
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Typical Performance Plots
All typical plots are based on TA = 25°C, VDD = 5V, CF = 1 nF, unless otherwise stated.
Figure 1: Sensitivity vs. Temperature
Figure 2: Zero Current Output Voltage vs. Temperature
Zero Current Output Voltage (VOUT(Q)) – V
Sensitivity (Sens) – mV/A
200
175
ACHS-7121
ACHS-7122
150
ACHS-7123
125
100
75
50
–40
–20
0
20
40
60
80
100
120
2.515
2.510
2.505
2.500
2.495
ACHS-7121
2.490
ACHS-7122
ACHS-7123
2.485
–40
–20
0
Temperature (TA) – °C
Figure 3: Nonlinearity vs. Temperature
20
40
60
Temperature (TA) – °C
80
100
120
Figure 4: Total Output Error at IPMAX vs. Temperature
0.30
8.0%
Total Output Error (ETOT) – %
0.28
0.26
Nonlinearity (NL) – %
0.24
0.22
0.20
0.18
0.16
0.14
0.12
0.10
0.08
ACHS-7121
0.06
4.0%
2.0%
0.0%
–2.0%
ACHS-7121
–4.0%
ACHS-7122
–6.0%
ACHS-7123
ACHS-7122
0.04
–8.0%
–40
ACHS-7123
0.02
0.00
–40
6.0%
–20
0
20
40
60
80
100
–20
0
20
40
60
Temperature (TA) – °C
80
100
120
120
Temperature (TA) – °C
Broadcom
ACHS-712x-DS101
9
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Figure 6: Supply Current vs. Supply Voltage
13.8
14.5
13.6
14.0
Supply Current (IDD) – mA
Supply Current (IDD) – mA
Figure 5: Supply Current vs. Temperature
13.4
13.2
13.0
12.8
13.5
13.0
12.5
110°C
12.0
25°C
–40°C
11.5
12.6
–40
–20
0
20
40
60
80
100
120
11.0
Temperature (TA) – °C
3
3.5
4
4.5
5
5.5
Figure 7: Output Voltage vs. Input Current
Figure 8: Power On Time vs. External Filter Capacitance
100
5.0
IP = IP(max)
4.0
Power On Time (tPO) – ȝs
Output Voltage (VOUT) – V
4.5
3.5
3.0
2.5
2.0
ACHS-7121
1.5
ACHS-7122
1.0
80
60
40
20
ACHS-7123
0.5
0.0
–30
0
–20
–10
0
10
20
30
0
Figure 9: Output Noise vs. External Filter Capacitance
2
4
6
8
10
External Filter Capacitance (CF) – nF
Input Current (IP) – A
Figure 10: Rise Time vs. External Filter Capacitance
30
10
25
Rise Time (tR) – ȝs
Output Noise (VN(RMS)) – mV
6
Supply Voltage (VDD) – V
1
ACHS-7121
ACHS-7122
20
15
10
5
ACHS-7123
0.1
0.01
Broadcom
IP = IP(max)
0
0.1
1
10
External Filter Capacitance (CF) – nF
100
0
2
4
6
8
10
External Filter Capacitance (CF) – nF
ACHS-712x-DS101
10
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
Definition of Electrical Characteristics
The ACHS-7121/7122/7123 product series is a Hall Effect
current sensor that outputs an analog voltage proportional
to the magnetic field intensity caused by the current flowing
through the input primary conductor. Without the magnetic
field, the output voltage is half of the supply voltage. The
sensor can detect both DC and AC current.
Figure 11: Nonlinearity Calculation
VOUT
Max¨
from BFL
Min¨
from BFL
Ratiometric Output
IP(MIN)
The output voltage of the ACHS-7121/7122/7123 series is
ratiometric or proportional to the supply voltage. The
sensitivity (Sens) of the device and the quiescent output
voltage changes when there is a change in the supply
voltage (VDD). For example, when the VDD is increased by
10% from 5V to 5.5V in the ACHS-7122, the quiescent
output voltage changes from 2.5V to 2.75V and the
sensitivity also changes from 100 mV/A to 110 mV/A.
The output sensitivity (Sens) is the ratio of the output
voltage (VOUT) over the input current (IP) flowing through the
primary conductor. It is expressed in mV/A. When an
applied current flows through the input primary conductor, it
generates a magnetic field which the Hall IC converts into a
voltage. The proportional voltage is provided by the Hall IC
which is programmed in the factory for accuracy after
packaging. The output voltage has a positive slope when an
increasing current flows through pins 1 and 2 to pins 3 and
4. Sensitivity Error (ESENS) is the difference between the
measured Sensitivity and the Ideal Sensitivity expressed as
a percentage (%).
Nonlinearity
Nonlinearity is defined as half of the peak-to-peak output
deviation from the best-fit line (BFL), expressed as a
percentage of the full-scale output voltage. The full-scale
output voltage is the product of the sensitivity (Sens) and full
scale input current (IP).
[(Max¨ from BFL – Min¨ from BFL) / 2]
Sens X full scale I P
Broadcom
IP(MAX)
BFL
Zero Current Output Voltage
Sensitivity
NL(%) =
full scale IP)
× 100%
This is the output voltage of ACHS-7121/7122/7123 when
the primary current is zero. Zero current output voltage is
half of the supply voltage (VDD/2).
Zero Current Output Error
This the voltage difference between the measured output
voltage and the ideal output voltage (VDD/2) when there is
no input current to the device.
Total Output Error
Total output error in percentage is the difference between
the measured output voltage at maximum input current
(IPMAX) and the ideal output voltage at IPMAX divided by the
ideal output voltage at IPMAX.
E TOT (%) =
Measured VOUT @ I PMAX – Ideal V OUT @ I PMAX
× 100%
Ideal VOUT @ I PMAX
Power-On Time
This is the time required for the internal circuitry of the
device to be ready during the ramping of the supply voltage.
Power on time is defined as the finite time required for the
output voltage to settle after the supply voltage reached its
recommended operating voltage.
ACHS-712x-DS101
11
ACHS-7121/7122/7123 Data Sheet
FILTER Pin
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
Figure 12: Land Pattern for 4 mm Creepage
The ACHS-7121/7122/7123 has a FILTER pin for improving
the signal-to-noise ratio of the device. This eliminates the
need for an external RC filter for the VOUT pin of the device,
which can cause attenuation of the output signal. A ceramic
capacitor, CF, can be connected between the FILTER pin to
GND.
7.1
(0.280)
Application Information
1.50 (0.059)
PCB Layout
The design of the printed circuit board (PCB) should follow
good layout practices, such as keeping bypass capacitors
close to the supply pin and use of ground and power planes.
A bypass capacitor must be connected between pins 5 and
8 of the device. The layout of the PCB can also affect the
common-mode transient immunity of the device due to stray
capacitive coupling between the input and output circuits. To
obtain maximum common-mode transient immunity
performance, the layout of the PCB should minimize any
stray coupling by maintaining the maximum possible
distance between the input and output sides of the circuit
and ensuring that any ground or power plane on the PCB
does not pass directly below or extend much wider than the
body of the device.
0.64(0.025)
Effect of PCB Layout on Sensitivity
The trace layout on the input pins of ACHS-7121/7122/7123
affects the sensitivity. It is recommended that the PCB trace
connection to the input pins covers the pins fully, as shown
in Figure 13.
Figure 13: Recommended Trace Layout on Input Pins
PCB
TRACE
IP-
IP+
PCB
TRACE
Land Pattern for 4 mm Board Creepage
For applications that require PCB creepage of 4 mm
between input and output sides, the land pattern in
Figure 12 can be used.
Broadcom
ACHS-712x-DS101
12
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Isolation and
Low-Resistance Current Conductor
ACHS-7121/7122/7123 Data Sheet
When the connection to the input pin only covers the vertical
portion of the input pin, there is a sensitivity variation of
about –0.6% versus recommended PCB trace layout (as
shown in Figure 14).
Figure 14: Vertical Portion Connection
PCB
TRACE
IP-
PCB
TRACE
IP+
Thermal Consideration
The evaluation board used in the thermal characterization is
shown in Figure 16. Inputs IP+ and IP– are each connected
to input plane of 2 oz. copper with 300 mm2 total area
(including top and bottom planes). The output side GND is
connected to a ground plane of 2 oz. copper with 460 mm2
total area (including top and bottom planes). The 2 oz.
copper enables the board to conduct higher current and
achieve good thermal distribution in a limited space.
Figure 16: Broadcom Evaluation Board—Top Layer
When the connection to the input pin only covers the
horizontal portion of the input pin, there is a sensitivity
variation of about +1.2% versus recommended PCB trace
layout (as shown in Figure 15).
Figure 15: Horizontal Portion Connection
PCB
TRACE
IP-
IP+
PCB
TRACE
Figure 17: Broadcom Evaluation Board—Bottom Layer
Broadcom
ACHS-712x-DS101
13
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