User Guide 061
ISL70617SEHEV1Z Evaluation Board User Guide
Description
The ISL70617SEHEV1Z evaluation board is designed to assess
the performance of the
ISL70617SEH
differential input,
differential output, precision instrumentation amplifier
(in-amp). With separate supply rails for the input and output
stages and gain ranging from 0.1 to 10,000, this in-amp is
ideal for a wide variety of applications. The gain accuracy is
limited only by the matching of the gain resistors and the
output is capable of driving rail-to-rail.
Key Features
• Separate input and output supplies allow signals riding on a
high common-mode voltage to be level shifted to a low
voltage device.
• Banana jack connectors for simple power supply
connections.
• Multiple connectors to easily access V
IN
and V
OUT
Specifications
The boards are designed to operate under the following
conditions.
• Power supply range:
- Input: 8V (±4V) to 36V (±18V)
- Output: 3V (±1.5V) to 36V (±18V)
• Common-mode Input voltage range: V
EE
+ 3V to V
CC
- 3V
• Differential input voltage range: ±3V (Note
1)
• Output voltage range: ±3V (Note
1)
• Operating temperature range: -55°C to +125°C
NOTE:
1. The input and output voltage range may also be limited by the
power supply voltages.
Reference Documents
•
ISL70617SEH
Datasheet
Ordering Information
ORDERING NUMBER
ISL70617SEHEV1Z
OUTPUT
Differential
TYPE
Evaluation Board
V+
GND
V-
V+ OUT
GND
V - OUT VCMO/VREF GND
R
22
IN+
R
18
R
IN
R
1
AV = R
FB
/R
IN
RANGE FROM
0.1 TO 10,000
R
FB
R
3
IN-
R
21
R
17
IN+
V
CC
+R
IN
+R
IN
SENSE
-R
IN
SENSE
-R
IN
V
CO
+V
FB
+V
OUT
-V
OUT
-V
FB
+V
OUT
+R
FB
+R
FB
SENSE
ISL70617SEH
-R
FB
SENSE
-R
FB
V GND
EE
V
CMO
V
EO
-V
OUT
IN-
FIGURE 1. ISL70617SEH EVALUATION BOARD BLOCK DIAGRAM
November 19, 2015
UG061.0
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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User Guide 061
Functional Description
The schematic of the evaluation board is shown on
Figure 10.
The ISL70617SEHEV1Z contains the ISL70617SEH in-amp (U1),
supply decoupling capacitors (C
1
-C
12
, C
15
-C
17
), optional filter
capacitors (C
13
, C
14
, C
18
-C
21
), feedback gain resistor (R
1
), input
gain resistor (R
3
) and numerous filter, load and selection
resistors. Component values are listed in the BOM
page 7.
Inputs and Outputs
The input and output pins have BNC connectors (J9-J12) as well
as two pin headers (J13, J16) to allow the use of differential
probes. When testing the output voltage of the device under load,
it is recommended to attach the load to the BNC connector and
monitor the voltage from the differential probe.
The ISL70617SEHEV1Z includes the option for an anti-aliasing
filter on the output comprised of a 100Ω resistor (R
7
, R
8
) and
3300pF capacitor (C
14
, C
18
). The filter is recommended when
connecting the output directly to an ADC. When using the in-amp
in a gain less than 1, it is possible to add a low pass filter before
the input to compensate for the gain peaking at the limits of the
gain bandwidth product. Resistor locations (R
21
, R
22
) and
capacitors locations (C
19
, C
20
) can be used for this input filter.
Power Supplies
External power supplies are connected via the banana jack plugs
(J1-J8). Each plug is labeled to identify the corresponding supply,
ground, or reference voltage. The in-amp has two distinct sets of
power supplies; one on the input stage and one on the output
stage. The input and output supplies can be connected together
externally or powered separately. Using the separate supply
feature enables input signals riding on a high common-mode
voltage to be level shifted to a low voltage device such as an
Analog-to-Digital Converter (ADC). The operating voltage range is
±4V to ±36V for V
CC
/V
EE
and ±1.5V to ±36V on V
CO
/V
EO
. For
split supply operation, the common-mode voltage (V
CMO
) can be
connected externally to ground.
The supply voltage on the input stage must be 3V above the
maximum and 3V below the minimum input signal voltage. Note
that while the output stage is rail-to-rail, the feedback returns to
the input stage, which is not rail-to-rail. Therefore, the input
power supply must be 3V above and below the maximum and
minimum output signal as well. For more information, reference
“Setting the Power Supply Voltages” section in the
ISL70617SEH
datasheet.
Amplifier Configuration
The ISL70617SEH evaluation board schematic is in a closed loop
gain of 1 in the default configuration. To change the gain, simply
replace the R
3
input resistor and/or the R
1
feedback resistor.
The in-amp gain is calculated with the
Equation 1:
R
1
-
A
V
= ------
R
3
(EQ. 1)
R
1
and R
3
also limit the maximum signal size at the input and
output due to the amplifier architecture.
Table 1
shows the signal
limits for the boards at the preset resistor values. For more
information, refer to the “Setting the Feedback Gain R
FB
” and
“Setting the Input Gain R
IN
” section in the
ISL70617SEH
datasheet.
Figures 2
through
9
show several of the key performance curves
generated from the ISL70617SEHEV1Z.
TABLE 1. RECOMMENDED INPUT AND OUTPUT VOLTAGE LIMITS FOR A GIVEN SET OF GAIN RESISTORS
R
IN
(Ω)
30.1k
3.01k
301
301k
R
FB
(kΩ)
30.1
30.1
30.1
30.1
GAIN
1
10
100
0.1
MAX RECOMMENDED
V
IN
(V)
±2.0
±0.20
±0.020
±20
Max Recommended
V
OUT
(V)
±2.0
±2.0
±2.0
±2.0
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