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Application Note 1508
ISL281X7SOICEVAL1Z Evaluation Board User’s Guide
Introduction
The ISL281X7SOICEVAL1Z evaluation board is a design
platform containing all the circuitry needed to
characterize critical performance par ameters of the
ISL281X7 operational amplifiers in SOIC -8 package,
using a variety of user defin ed test circuits.
The ISL281X7 operational amplifiers feature low bias
current, low noise, and low offset and temper ature drift.
Reference Documents
• ISL28107 Data Sheet, FN6631
• ISL28117 Data Sheet, FN6632
• ISL28127 Data Sheet, FN6633
Evaluation Board Key Features
The ISL281X7SOICEVAL1Z is designed to enable the IC
to operate from a single supply, +4.5VDC to +40VDC or
from split supplies, ±2.25VDC to ±20V. The board is
configured for a single op amp connected for differential
input with a closed loop gain of 10. A single external
reference voltage (VREF) pin and provisions for a
user-selectable voltage divider-filter are included.
Power Supplies (Figure 1)
External power connections are made through the +V, -V,
VREF and Ground connections on the evaluation board.
F or single supply oper ation, the -V and Ground pins are
tied together to the power supply negative terminal. For
split supplies, +V and - V terminals connect to their
respective power supply terminals. De-coupling
capacitors C2 and C4 connect close to their respective
supplies, while two additional capacitors, C1 and C5, are
connected close to the part to filter out high f requency
noise. Anti-reverse diodes D1 and D2 protect the circuit
in the case of accidental polarit y reve rsal.
Amplifier Configuration (Figure 2)
The schematic of 1/2 of the op-amp with the components
supplied is shown in Figure 2. The circuit implements a
differential input amp with a closed loop gain of 10. The
circuit can operate from a single supply or from dual
supplies. The VREF pin must be connected to ground to
establish a ground referenced input for dual supply
operation, or can be externally set to any reference level for
single supply operation. VREF should not be left f loating.
C2
4.7µF
DNP
D2D1
R16
R4
C4
J8
J11
J9
J10
J7
J13
S1AB
4.7µF
S1AB
DNP
VREFV+V-
FIGURE 1. POWER SUPPLY CIRCUIT
IN-
IN+
RF
VREF
IN -
IN +
GND
100k
Ω
RREF+
VOUT
ISL281X7
VP
V-
0
Ω
VM
VCM
IN-
IN+
VREF
V+
RIN-
10k
Ω
RIN+
10k
Ω
-
+
100k
Ω
RL
DNP
FIGURE 2. BASIC AMPLIFIER CONFIGURATION
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 |Intersil (and design) is a regi s tered trademark of Intersil Americ as Inc .
Copyright Intersil Americas Inc. 2009. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
November 9, 2009
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User-selectable Options
(Figures 3 and 4)
Component pads are included to enable a variety of
user-selectable circuits to be added to the amplifier
VREF, inputs, outputs, and the amplifier feedback
loops. The Inputs (Figure 3) h ave additional resistor
and capacitor, and jumper placements for loading
and/or measurement of frequency sensitiv e
parameters.
The outputs (Figure 4) have ad ditional resistor and
capacitor placements for filtering and loading.
NOTE: Oper ational amplifiers are sensitiv e to output
capacitance and may oscillate. In the event of
oscillation, reduce output capacitance by using shorter
cables, or add a resistor in series with the output.
FIGURE 3. INPUT STAGE FIGURE 4. OUTPUT STAGE
IN- OUTNODEIN+
C3
R7
R5
J2
J1 R1
R6
R14
R2 R14
R3
R15
R10R8
R11R9
DNP DNP
DNP
DNP
DNP
DNP
DNP
OPEN
DNP
DNP
10k 100k
100k
10k
0
VREF
To Output
To IN+
To IN-
R13
R12
R18 J12
C6
R17
DNP
0
OPEN
TABLE 1. ISL281X7SOICEVAL1Z COMPONENTS PARTS LIST
DEVICE # DESCRIPTION COMMENTS
C2, C4 CAP, SMD, 0805, 4.7µF, 50V, 10%, X7R, ROHS Power Supply Decoupling
C1, C5 CAP, SMD, 0603, 0.01µF, 50V, 10%, X7R, ROHS Power Supply Decoupling
C3, C6 CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS User selectable capacitors - not populated
D1, D2 DIODE-RECTIFIER, 40V, 0.5A, ROHS Reverse Power Protection
U1 (ISL28107FBZ) OP AMP, SOIC, ROHS
U1 (ISL28117FBZ) OP AMP, SOIC, ROHS
U1 (ISL28127FBZ) OP AMP, SOIC, ROHS
R1-R4, R6-R8, R10, R13,
R14, R16, R17, R19, R20 RESISTOR, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER User selectable resistors - not populated
R5, R18 RES, SMD, 0603, 0Ω, 1/10W, TF, ROHS Zero ohm user selectable resistors
R9, R12 RES, SMD, 0603, 10k, 1/10W, 1%, TF, ROHS Gain resistors
R11, R15 RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS Gain resistors
Application Note 1508
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Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notic e. Accordingly, the
reader is caution ed t o v eri fy tha t th e Appl ica tio n No te or Tec hnical Brief is current before pro ceedi ng.
For information regarding Intersil Corporation and its products, see www.intersil.com
AN1508.0
November 9, 2009
Application Note 1508
FIGURE 5. ISL281X7SOICEVAL1Z TOP VIEW
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November 9, 2009
Application Note 1508
OUTPUT
IN +
OUTNODEIN+IN-
IN -
C2
4.7µF
DNP
R20
R19
D2D1
R18
U1
R16
R4
J4
J6
J5
J3
C3
R7
R5
C4
C1
C5
J12J2
J1
J8
J11
J9
J10
1
J7
J13
C6
R1
R6
R14
R2
R17
R12
R3
R15R13
R10R8
R11R9
10k
DNP
0.01µF
DNP
DNP
0.01µF
DNP
0
OPEN
100k
SOIC8
DNP
DNP
DNP
DNP
DNPDNP
OPEN
100k10k
DNP
0
DNP
S1AB
4.7µF
S1AB
DNP
5
6
7
8
3
4
1
2Generic
Pack.
VREF
VREFV+
V-
FIGURE 6. ISL281X7SOICEVAL1Z SCHEMATIC DIAGRAM
