Analog Devices Ad8411a Current Sense Amplifier User Guide

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

Table 2. VREF2 Pin Connections

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

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

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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