ANALOG DEVICES AD8235 Micropower Instrumentation Amplifier User Guide
- June 13, 2024
- Analog Devices
Table of Contents
AD8235ACBZ-EVALZ User Guide
UG-1478
Evaluating the AD8235 40 μA, Micropower Instrumentation Amplifier
FEATURES
Simple evaluation of the AD8235
CR2032 battery provision
On-board voltage reference using the LTC2063 low power amplifier
2 in × 1.35 in small form factor
APPLICATIONS
Fast and easy product evaluation and characterization Portable system applications
GENERAL DESCRIPTION
The AD8235ACBZ-EVALZ contains a CR2032 battery provision that is capable of
powering up the AD8235 40 μA, micropower instrumentation amplifier and the
LTC2063 low power operational amplifier. This feature allows the AD8235ACBZ-
EVALZ to be a standalone board ready for product evaluation.
The AD8235ACBZ-EVALZ design allows the user to easily adjust the gain
resistors and common discrete components on the board. The on-board male
headers set the AD8235ACBZ-EVALZ to different configurations using the jumper
shunt.
The AD8235ACBZ-EVALZ allows battery-powered configuration to showcase the
portable nature of the AD8235. In battery-powered configuration, the LTC2063
acts as the voltage reference for the single-supply configuration.
For full details on the AD8235, see the AD8235 data sheet, which must be
consulted in conjunction with this user guide when using the AD8235ACBZ-EVALZ.
EVALUATION BOARD PHOTOGRAPH
EVALUATION BOARD HARDWARE
SINGLE-SUPPLY OPERATION
A switch (S1) is provided on the AD8235ACBZ-EVALZ to select either a battery-
powered configuration or an external supply configuration. The AD8235ACBZ-
EVALZ is shipped in battery operated single-supply mode and is configured on
the P2, P3, and P5 jumpers.
ON-BOARD AD8235
The AD8235 shutdown pin (SDN) can allow continuous operation of the AD8235, or
this pin can interface to allow a microcontroller to be set when the AD8235
must operate in shutdown mode to conserve further energy.
Gain Adjustment
The AD8235 gain is pin-selectable where the gain (G) = 5 (default) and where
the gain resistor (RG) is unpopulated. The AD8235 gain is resistor dependent.
The resistor is connected between the RG pins. Table 1 provides calculated
gains for the AD8235. See the
AD8235 data sheet for the gain equation.
Table 1. AD8235 Gain Resistor Values
| 1% Standard Value of RG (kΩ) | Calculated Gain |
|---|
422
210
140
105
84.5
28
9.31
4.42
2.15| 6.0
7.0
8.0
9.0
10.0
20.0
50.1
100.0
200.3
COMPONENT LOCATIONS
See Figure 4 for the AD8235ACBZ-EVALZ component layout, connector locations,
and male header locations.
LOAD RESISTOR
Although not required for normal operation, a load resistor can be inserted at
Position R7.
Voltage Reference or Offset Adjustment
The default configuration of the AD8235ACBZ-EVALZ reference is set on the
midsup ply level driven by the LTC2063.
The on-board voltage reference can be set at the P2 jumper to power up the
LTC2063, and at the P3 jumper to connect the LTC2063 OUT pin to the AD8235 REF
pin. See Figure 2 for the schematic design of the on-board voltage reference.
The LTC2063 features a shutdown control pin (SHDN) to disable the device. The
2063SD header on the AD8235ACBZ-EVALZ connects the LTC2063 SHDN pin to either
the +VS pin or the GND1 pin of the AD8235ACBZ-EVALZ, and can interface to a
microcontroller. See Table 2 for the LTC2063 options.
Table 2. Jumpers and Switch Configuration Options
| Jumper | Function | Default Position |
|---|---|---|
| 8235SD | Allows the AD8235 SDN pin to connect to either the +VS input or the |
−VS input on the
AD8235ACBZ-EVALZ.| EN
2063SD| Allows the LTC2063 SHDN pin to connect to either the +VS input or the
GND1 input on the
AD8235ACBZ-EVALZ.| EN
P1| Connects the LTC2063 V + pin to the power supply to power up the
LTC2063.| Installed
P2| Allows the AD8235 REF pin to connect to either the LTC2063 OUT pin or the
GND1 pin
on the AD8235ACBZ-EVALZ.| Position 1, connected to the LTC2063 OUT pin
P3| Connects the AD8235 –VS pin to the GND1 pin on the AD8235ACBZ-EVALZ for
single supply
operation.| Installed
S1| Allows the AD8235ACBZ-EVALZ to be powered up by the CR2032 battery.|
Position 1, battery not connected to the AD8235 +VS pin or the LTC2063 V +
pin
Table 3. AD8235ACBZ-EVALZ Input/Output Pins and Function Descriptions
| Input/Output Pin | Function |
|---|
+VS and –VS
GND1 and GND2
+IN and −IN
REF
VOUT| Positive and negative rails of the amplifiers.
Ground for the board.
Positive and negative AD8235 inputs.
Reference input for the AD8235.
AD8235 output.
AD8235ACBZ-EVALZ SCHEMATIC AND ARTWORK
ORDERING INFORMATION
BILL OF MATERIALS
Table 4.
Reference Designator| Description| Manufacturer| Part
Number
---|---|---|---
R5
R1, R2
R3, R4, R6
C6, C8
C1, C5, C7
P1, P3
P2, 8235SD, 2063SD
S1
+VS, −VS, +IN, −IN, GND1, GND2, VOUT
BAT1
U2
U1| Precision thin film chip resistor, 4.42 kΩ, R0603
Precision thin film chip resistors, 510 kΩ, R0603
Surface mount device (SMD) resistor chips, 0 Ω, R0603
X5R ceramic capacitors, 10 μF, R0603
X7R ceramic capacitors, 0.1 μF, R0603
2-position, male printed circuit board (PCB) headers
3-position, male PCB headers
Subminiature single-pole double throw (SPDT) switch
Turret style test points
CR2032 battery holder
Low bias current (IB), zero drift operational amplifier
Micropower instrumentation amplifier, 40 μA| Panasonic
TE Connectivity
Vishay
TDK
Kemet
SAMTEC
SAMTEC
C&K
Keystone Electronics
Memory Protection Devices
Analog Devices
Analog Devices| ERJ-3EKF4421V
CPF0603B510KE1
CRCW0603000ZRT1
C1608X5R1A106K080AC
C0603C104K4RAC
TSW-102-08-G-S
TSW-103-08-T-S
JS102011JCQN
1502-2
BHX1-2032-PC
LTC2063ISC6#TRMPBF
AD8235ACBZ-P7
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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