ANALOG DEVICES AD8411A Current Sense Amplifier User Guide
- June 11, 2024
- Analog Devices
Table of Contents
User Guide | EVAL-AD8411A
UG-2112
Evaluating the AD8411A, −2 V to 70 V Wide Input Voltage Range, 2.7 MHz High
Bandwidth,
Current-Sense Amplifier with PWM Rejection and Gain 50 V/V
FEATURES
► Enables quick breadboarding and prototyping
► Easily configurable for unidirectional or bidirectional operation
► Includes provision for current-sense shunt resistor
► Easy connection to test equipment
► Includes provisions for an input filter and an output filter
► Decoupled supply line
EVALUATION KIT CONTENTS
► AD8411ARM-EVALZ evaluation board
DOCUMENTS NEEDED
► AD8411A data sheet
GENERAL DESCRIPTION
The AD8411ARM-EVALZ is designed to aid in the evaluation of the AD8411A
current-sense amplifier. These boards are designed for easy configuration of
different modes of operation and allow flexibility with loads. A shunt
resistor (R1), with a maximum standard size of 2818, can be soldered to the
board.
The AD8411ARM-EVALZ accommodates the AD8411A in a mini small outline package
(MSOP).
Full specifications on the AD8411A are
available in the AD8411A data sheet available from Analog Devices, Inc., and
must be consulted with this user guide when using the AD8411ARM-EVALZ
evaluation board.
REVISION HISTORY
4/2023—Revision 0: Initial Version
AD8411ARM-EVALZ EVALUATION BOARD PHOTOGRAPHS
QUICK START
By default, VREF1 is connected to VS, and VREF2 is connected to the GND pin. This split supply configuration sets the output to midsupply and allows bidirectional current sensing. Connect 5 V to the VS test point on the evaluation board, connect the ground of the supply to the AGND test point on the evaluation board, and place a 0.04 V differential voltage between the +VIN test point and the −VIN test point on the evaluation board. This small 0.04 V differential input voltage represents the voltage drop across the shunt resistor that is used in the application.
VOUT = 2.5V+ VDIFF × GAIN (1)
After the evaluation board is powered, the output reads as:
4.5V = 2.5V+ 0.04V × 50V/V (2)
Then swap the input differential voltage leads (move the lead on the
+VIN test point to the −VIN test point and move the lead that was
on the −VIN test point to the +VIN test point). The output then reads as:
0.5V = 2.5V− 0.04V × 50V/V (3)
POWER SUPPLIES
The AD8411A has a power-supply operating range from 2.9 V to 5.5 V. Power is
applied to the VS test point. Decoupling capacitors of 10 µF and 0.1 µF are
preinstalled on the evaluation board.
COMPONENTS
The AD8411A can be used for a variety of
current monitoring applications. The AD8411ARM-EVALZ has a provision for a
currentsense shunt resistor with a maximum standard size of 2818. There are
also provisions with 0805 footprints for a capacitive-load, a resistive load,
an input electromagnetic interference (EMI) filter, an output
filter, and provisions to set the reference voltage. Terminal blocks (P1 and
P2) are provided to allow easy wiring and evaluation. Table 1. VREF1 Pin
Connections
SETTING THE REFERENCE VOLTAGE
Three resistor spaces (R5, R6, and R7) are on the left side of the AD8411A on
the AD8411ARM-EVALZ. These three resistors are used to set VREF2. Fill only
one of these resistor spaces at a time with a 0 Ω, 0805 resistor. See Table 2
for the resistors that must be
filled with 0 Ω to resistor to set VREF2.
Three resistor spaces (R8, R9, and R10) are on the right side of the AD8411A
on the AD8411ARM-EVALZ. These three resistors are used to set VREF1. Fill only
one of hese resistor spaces at a time with a 0 Ω, 0805 resistor. See Table 1
for the resistors that must be filled with 0 Ω to resistor to set VREF1.
Table 1. VREF1 Pin Connections
Pin R8 R9 R10
vs| | |
GND| X| ✓| X
EXT1| ✓| X| X
Table 2. VREF2 Pin Connections
Pin R5 R6 R7
vs| | |
GND| X| ✓| X
EXT2| ✓| X| X
Unidirectional Operation
For unidirectional operation, the output can be set at the negative rail (near
ground) or at the positive rail (near the supply voltage) when the
differential voltage is 0 V. To set the AD8411ARM-EVALZ for a ground-
referenced output, solder the 0 Ω resistor on the left side of the AD8411A in
the R6 space and the 0 Ω resistor on the right side of the AD8411A in the R9
space.
To set the AD8411ARM-EVALZ for a supply voltage referenced output, solder the
0 Ω resistor on the left side of the AD8411A in the R7 space and the 0 Ω
resistor on the right side of the AD8411A in the R10 space.
Bidirectional Operation
For a bidirectional operation, the output is typically set at half-scale for
an equal range in both directions. To configure the output to be at midsupply
in the presence of 0 A of current through the shunt resistor on the AD8411ARM-
EVALZ, solder the 0 Ω resistor on the left side of the AD8411A in the R6 space
and the 0 Ω resistor on the
right side of the AD8411A in the R10 space.
By default, the output of the AD8411ARM-EVALZ is biased at midsupply.
Table 3 shows which resistor must be filled with 0 Ω resistor to set the
AD8411ARM-EVALZ for different operations. In unidirectional operation, it can
be ground- eferenced output and supply
QUICK START
voltage-referenced output, whereas, in the bidirectional operation, the output
can be set to midsupply.
Table 3. Operation Connection
Mode R6 R7 R9 R10
UNIDIRECTIONAL Ground Referenced Supply Voltage Referenced| ii. x| X| rna. x|
1 x ai.
BIDIRECTIONAL Midsupply| ✓| X| X| ✓
External Referenced Output
An external supply can also be used to set the reference voltage. To bias the
output to a single external supply, solder a 0 Ω, 0805 resistor in the R4
space. Then, solder the 0 Ω resistor on the left side of the AD8411A in the R5
space and solder the 0 Ω resistor on the right side of the AD8411A in the R8
space. The external supply voltage can then be applied to any one of the EXTx
test points onthe evaluation board, and this configuration biases the output
to the external supply.
The external supply can also be divided by 2 and used as a reference level.
For this reference level, solder the 0 Ω resistor on the left side of the
AD8411A in the R6 space, desolder the resistor in the R4 space, and solder the
0 Ω resistor on the right side of the AD8411A in the R8 space. Apply the
external supply to the EXT1 test point or EXT1 terminal block input, and the
output of the AD8411A is referenced to half of the external supply.
Two separate external supplies can also be used to set the reference for the
output. Desolder the 0 Ω resistor from the R4 space. Solder the 0 Ω resistor
on the left side of the
AD8411A in the R5 space and solder the 0 Ω resistor on the right side of the
AD8411A in the R8 space. Apply the first external supply, VEXT1, to the EXT1
test point or EXT1 terminal block input. Apply the second external supply,
VEXT2, to the EXT2 test point or EXT2 terminal block input. This configuration
references the output to:
INPUT FILTER
The AD8411ARM-EVALZ includes provisions for the components necessary for an
input filter. By default, R2 and R3 are 0 Ω, 0805 resistors and C1, C2, and C3
are left unpopulated. It is requiredto filter at the input of the device to
reduce EMI. The EMI specifications vary depending on the application.
Filtering at the input must be referred if the output cannot be filtered
because filtering at the output changes the low output impedance seen by the
components attached to the output of the AD8411A. The +IN and –IN inputsof the
AD8411A has balanced input bias currents. This means that the input series
resistors, R2 and R3, must be the same measured value not to have a large
offset voltage added to the output of thedevice as a result of R2 and R3. It
is recommended to keep R2 and R3 below 100 Ω.
The EMI filter has two different bandwidths, common-mode (BWCM) and
differential (BWDIFF). The differential bandwidth defines the frequency
response of the filter with a differential input signal applied between the
two inputs of the amplifier, which are +IN and −IN. C1 and C3 must be the same
value for the following equations.
The −3 dB differential bandwidth for the filter is:
The common-mode bandwidth defines what a common-mode RF signal experiences
between ground and the +IN and –IN inputs of the amplifier tied together.
The −3 dB common-mode bandwidth for the filter is:
Keep the resistor values to a 1% tolerance and the filter capacitors to a 5%
tolerance to assist with reducing AC common-mode rejection (CMR) errors.
Choose C2 to be at least 10× larger than C1 or C3 to reduce AC CMR errors,
which are caused by component mismatching.
Figure 1 shows the top view and Figure 2 shows the bottom view of the
AD8411ARM-EVALZ. Figure 4 shows the default schematic of the AD8411ARM-
EVALZ. The otted lines in the AD8411ARMEVALZ schematic are routed under the
printed circuit board (PCB).
EVALUATION BOARD SCHEMATIC
ORDERING INFORMATION
BILL OF MATERIALS
Item| Quantity| Reference Designator| Part Description|
Manufacturer, Part Number
---|---|---|---|---
1
2
3
4
5
6
7
8
9
10
11
12
13
14
| 1
2
4
1
1
4
1
1
6
4
5
1
5
1| U1
+VIN, −VIN
AGND, GND1, GND2,
GND3
C4
C5
EXT1, EXT2, OUT, VS
P1
P2
R2, R3, R4, R6, R10, R11
Standard Grip
C1, C2, C3, C6, C7
R1
R5, R7, R8, R9, R12
TP1| IC, High voltage, high bandwidth, current-sense amplifier,automotive
Connectors-PCB, test point white
Connectors-PCB, test point black
Capacitor, CER, 0.1 μF, 50 V, 10%, X7R, 1206
Capacitor, TANT, 10 μF, 16 V, 10%, 3528-20
Connectors-PCB, test point red
Connector-PCB, terminal block VERT, 5 mm pitch
Connector-PCB, terminal block, 5 mm pitch, 3.5 mm
solder tail
Resistors, SMD, 0 Ω, 1/10 W, 0805
Miscellaneous, Bumper cylindrical, size 0.312″ Dia
(7.92 mm), thickness 0.215″ (5.46 mm), black with
adhesive
Not installed, Capacitors, C0805
Not installed, Resistor, 2818
Not installed, Resistors, R0805
Connector-PCB, test point black| Analog Devices Inc., AD8411AWBRMZ
Keystone Electronics, 5002
Keystone Electronics, 5001
Yageo, CC1206KRX7R9BB104
AVX Corporation, TAJB106K016RNJ
Keystone Electronics, 5000
On Shore Technology, OSTTC030162
On shore Technology, OSTTC040162
Multicomp (SPC), MC 0.1 W 0805 0R
3M, SJ61A6
Not Applicable
Vishay, WSHM2818R0500FEA
Not Applicable
Keystone Electronics, 5001
ESD Caution
ESD (electrostatic discharge) sensitive device. Charged devices and
circuit boards can discharge without detection. Although this product features
patented or proprietary protection circuitry, damage may occur on devices
subjected to high energy ESD. Therefore, proper ESD precautions should be
taken to avoid performance degradation or loss of functionality.
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