an1753

Application Note 1753
ISL28617VYXXEV1Z User’s Guide
Introduction
The ISL28617VYXXEV1Z evaluation board is designed to assess
the ISL28617 instrumentation amplifier’s (in-amp) performance
with Bulk Metal® Foil resistors from Vishay Precision Group. With
a differential input voltage range up to ±34V, a supply voltage range
of 8V (±4V) to 40V (±20V) and gain ranging from 0.1 to 10,000,
this precision in-amp is ideal for a wide variety of applications. It
features differential inputs and outputs, and can drive the output
rail-to-rail. The gain accuracy is limited only by the matching of
the gain resistors. Reference: Vishay Precision Group’s foil
resistors at http://www.vishaypg.com/ppg?63209.
The FRSM series Bulk Metal® Foil ultra-high precision resistors
have a tolerance of 0.01% and a temperature coefficient (TCR) of
0.2 ppm/°C, giving exceptional gain accuracy that is ideal for
high end applications. The foil resistors are capable of achieving
tighter absolute and ratio tolerances than any other technology.
The real value of foil resistors is their unmatched stability
through temperature excursions, load life and extraordinary
thermal and environmental stresses, resulting in far more stable
gain ratios. Another important feature of the Bulk Metal® Foil
technology is the lowest current noise of any resistor technology
(<- 40 dB). The combination of foil resistors’ low current noise
and the exceptional low-noise performance of the ISL28617
amplifier make this the perfect solution for noise critical
precision applications.
The board is configured for ease of use, but allows for more
complex variations to fit the user’s need. The evaluation board
includes test points (VCC, VEE, and GND) for the power supply
inputs, and is configured for operation from split supplies
between ±4V to ±20V. There are two pairs of test points for the
differential input and output as well (VIN+, VIN-, VOUT+, and VOUT-).
The board is available in three different gain configurations: 0.25,
10 and 100. Ordering information is shown in Table 3.
Reference Documents
• ISL28617 Data sheet, FN6562
• FRSM Vishay Foil Resistor Data sheet, Document Number:
63209
Power Supplies
supply voltages for the three standard boards. For more
information, reference “Setting the Power Supply Voltages” on
page 13 of the ISL28617 data sheet.
If the user wants to control the output supplies separately, the R3
and R5 resistors must be removed, and the VCO (TP2) and VEO
(TP6) test points are used for the positive output supply and
negative output supply respectively (reference evaluation board
schematic in Figure 4). Single supply operation requires
removing R7 and attaching the desired common mode voltage to
the VREF (TP10) test point. 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 rail-to-rail output stage can be powered from
the same supplies as the ADC while preserving the in-amp’s
maximum input dynamic range. Once again, the positive input
power supply must be 3V above the maximum output signal, and
the negative input power supply must be 3V below the minimum
output signal.
Amplifier Configuration
The ISL28617 evaluation board schematic is shown in Figure 4
with a closed loop gain of 10 and split supply operation with
input and output supplies tied together. Other gain options are
0.25 and 100, with the required resistor and capacitor changes
listed in Table 1. The in-amp gain is controlled through R1 and
R2, the feedback and input resistors, with the following simple
formula:
R1
A V = ------R2
(EQ. 1)
R1 and R2 also limit the maximum signal size at the input and
output due to the amplifier architecture. Table 2 shows the signal
limits for the boards at the preset resistor values. For more
information, refer to “Setting the Feedback Gain RFB" and
“Setting the Input Gain RIN” on page 13 of the ISL28617 data
sheet.
The evaluation board allows the user to add an optional low pass
RC filter to the signal path. R8, R9, and C6 create a filter on the
output of the in-amp, while R10, R11, and C7 create a filter on
the input. The gain of 0.25 board option includes a filter on the
input to avoid gain peaking at the limits of the gain bandwidth
product.
External power connections are made to the positive supply rail
(TP1), the negative supply rail (TP9), and ground (TP4) for split
supply operation. The operating voltage range is ±4V to ±20V.
The in-amp has two distinct sets of power supplies; one on the
input stage and one on the output stage. For the evaluation
board, the output stage supplies are tied to the input stage
supplies, and the common mode voltage is tied to ground. The
supply voltage on the input stage must be 3V above and below
the maximum and minimum input signal voltage, respectively.
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. Table 2 provides suggested
September 26, 2012
AN1753.2
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
Copyright Intersil Americas Inc. 2012. All Rights Reserved.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
Application Note 1753
TABLE 1. COMPONENTS PARTS LIST
DEVICE #
VALUE
DESCRIPTION
TABLE 2. SUGGESTED INPUT VOLTAGE AND POWER SUPPLY LIMITS
GAIN
SUGGESTED
VIN LIMIT
OVERLOAD
VIN LIMIT
SUGGESTED
SUPPLY
VOLTAGE
C1-C5
0.01µF
Decoupling Capacitors
C6
Open
Optional Output Filter Capacitor
0.25
±10V
±12V
±15V
C7
Open
Optional Input Filter Capacitor
10
±1V
±1.2V
±15V
1.2pF
Input Filter Capacitor (G = 0.25)
100
±0.1V
±0.12V
±15V
D1, D2
S1A
Reverse Power Protection
R1
30kΩ
Feedback Gain Resistor (G = 0.25)
120kΩ
Feedback Gain Resistor (G = 10, 100)
120kΩ
Input Gain Resistor (G = 0.25)
12kΩ
Input Gain Resistor (G = 10)
1.2kΩ
Input Gain Resistor (G = 100)
R3, R5, R7
0Ω
User Selectable Resistors
R8, R9
0Ω
Optional Output Filter Resistors
R10, R11
0Ω
Optional Input Filter Resistors
49.9kΩ
Input Filter Resistors (G = 0.25)
R4, R6
1MΩ
Ground Input for Stability
U1
ISL28617
TSSOP 24-Pin Package
R2
TABLE 3. ORDERING INFORMATION
BOARD PART NUMBER
GAIN
TYPE
ISL28617VY25EV1Z
0.25
Eval Board
ISL28617VY10EV1Z
10
Eval Board
ISL28617VY100EV1Z
100
Eval Board
ISL28617VYXXEV1Z Evaluation Board Layout
FIGURE 1. TOP LAYER
2
FIGURE 2. BOTTOM LAYER
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Application Note 1753
ISL28617VYXXEV1Z Evaluation Board Layout
(Continued)
FIGURE 3. ASSEMBLY DRAWING
ISL28617VYXXEV1Z Schematic
IN-
IN+
-VFB
+VOUT
-VOUT
1MΩ
0Ω
R6
R11 (NOTE)
0Ω
R10 (NOTE)
TP9
TP6
15
14
VEO
13
VEE
C5
+VFB
VREF
TP10
D2
VEO
0.01µF
VCO
16
0Ω
VEE
0Ω
C4
VCC
R7
0.01µF
19
12kΩ
-RIN SENSE
0Ω
0.01µF
R8
-RFB SENSE
20
VCMO 17
12
C2
0Ω
0.01µF
R3
C1
D1
+RFB SENSE +RIN SENSE
21
8 GND
11
VCO
+RIN
-RIN 18
10
TP2
+RFB
OPEN
22
7 -R
FB
9
TP1
DNC
R9
VCC
DNC
C7 (NOTE)
23
R5
6
IN-
24
R2 (NOTE)
5
120kΩ
R1 (NOTE)
4
IN+
TP8
0.01µF
3
DNC
U1
ISL28617
24 LD TSSOP
C3
2
NC
0Ω
1
1MΩ
R4
TP7
C6
OPEN
VOUT+
GND
TP3
TP4
VOUT-
NOTE: COMPONENT VALUES FOR AV = 10
BOARD ONLY. SEE TABLE 1 FOR VALUES
USED ON AV = 0.25 AND AV = 100 BOARDS.
TP5
FIGURE 4. ISL28617VY10EV1Z (AV = 10) EVALUATION BOARD SCHEMATIC
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Application Note 1753
TABLE 4. BILL OF MATERIALS FOR AV = 10 BOARD (ISL28617VY10EV1Z)
PART #
REF DES
QTY
DESCRIPTION
MANUFACTURER
GRM39X7R103K050
C1-C5
5
CAP, SMD, 0603, 0.01µF, 50V, 10%, X7R, Murata
ROHS
DNP
C6, C7
0
DO NOT POPULATE
5000
TP1, TP9
2
CONN-MINI TEST POINT, VERTICAL, RED, Keystone
ROHS
5001
TP4
1
CONN-MINI TEST POINT, VERTICAL, BLK,
ROHS
Keystone
5002
TP7, TP8
2
CONN-MINI TEST POINT, VERTICAL,
WHITE, ROHS
Keystone
5004
TP3, TP5
2
CONN-MINI TEST POINT, VERTICAL, YEL,
ROHS
Keystone
S1A
D1, D2
2
DIODE-RECTIFIER, SMD, 2P, SMA, 50V,
1A, 1.4W, ROHS
Fairchild
ISL28617FVZ
U1
1
IC-40V R/R OUTPUT ADC DRIVER, 24P,
TSSOP, 4X5, ROHS
Intersil
ERJ-3GEY0R00V
R3, R5, R7-R11
7
RES, SMD, 0603, 0Ω, 1/10W, TF, ROHS
Panasonic
ERJ-3EKF1004V
R4, R6
2
RES, SMD, 0603, 1M, 1/10W, 1%, TF,
ROHS
Panasonic
Y4027120K000B9W
R1
1
RES-Z1 PRECISION, SMD, 2515, 120k,
3/4W, 0.1%, FOIL, ROHS
Vishay
Y402712K0000B9W
R2
1
RES-Z1 PRECISION, SMD, 2515, 12k,
3/4W, 0.1%, FOIL, ROHS
Vishay
DNP
TP2, TP6, TP10
0
DO NOT POPULATE
Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is
cautioned to verify that the Application Note or Technical Brief is current before proceeding.
For information regarding Intersil Corporation and its products, see www.intersil.com
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