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ISL281x8EVAL1Z Evaluation Board User’s Guide
Application Note
August 14, 2007
Introduction
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R20
• ISL28138 Data Sheet, FN6336
R1
0
V+
C1
+
4.7µF
D1
R24
R21
C2
+
4.7µF D2 0
Reference Documents
J1
V-
0
The ISL28138 and ISL28148 high-speed operational
amplifiers feature low power consumption, while the
ISL28158 and ISL28168 operational amplifiers feature
ultra-low power consumption. All op amps have rail-to-rail
output drive capability and are designed to operate with a
single lithium cell or two Ni_Cd batteries.
J2
The ISL281x8EVAL1Z evaluation board is a design platform
containing all the circuitry needed to characterize critical
performance parameters of the ISL281x8 operational
amplifiers, using a variety of user defined test circuits.
J3
and V- terminals connect to their respective power supply
terminals. De-coupling capacitors C1 andC2 connect to
ground through R1 and R21 0Ω resistors. Resistors R20 and
R24 are 0Ω but can be changed by the user to provide
additional power supply filtering, or to reduce the voltage
rate-of-rise to less than ±1V/µs. Two additional capacitors,
C3 and C4 are connected close to the part to filter out high
frequency noise. Anti-reverse diodes D1and D2 protect the
circuit in the case of accidental polarity reversal.
0
®
• ISL28148 Data Sheet, FN6337
C4
C3
• ISL28158 Data Sheet, FN6377
0.1µF
0.1µF
• ISL28168 Data Sheet, FN6378
VM
Evaluation Board Key Features
FIGURE 1. POWER SUPPLY CIRCUIT
The ISL281x8EVAL1Z is designed to enable the IC to
operate from a single supply, +2.4VDC to +5.5VDC or from
split supplies, ±1.2VDC to ±2.75V. The board is configured
for a single op amp connected for differential input with a
closed loop gain of 10. It also contains a single external
reference voltage (VREF) pin and provisions for a
user-selectable voltage divider (filter are included).
Amplifier Configuration (Figure 2)
The schematic 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 can be connected to ground to establish a ground
referenced input for split supply operation, or can be
externally set to any reference level for single supply
operation.
Power Supplies (Figure 1)
External power connections are made through the V+, Vand Ground connections on the evaluation board. For single
supply operation, the V- and Ground pins are tied together to
the power supply negative terminal. For split supplies V+
RF
VP
RIN-
IN-
IN-
V+
10kΩ
RIN+
IN+
VCM
GND
IN+
0Ω
0Ω
VOUT
V-
+
VM
10kΩ
IN+
VREF
ISL281x8
100kΩ
IN -
VREF
VP
RREF+
RL
100kΩ
10kΩ
10kΩ
FIGURE 2. BASIC AMPLIFIER CONFIGURATION
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Application Note 1350
User-selectable Options (Figures 3 and 4)
The output (Figure 4) has a 10kΩ load resistor to ground,
and has additional resistor and capacitor placements for
loading.
Component pads are included to enable a variety of
user-selectable circuits to be added to the amplifier inputs,
the VREF input, outputs and the amplifier feedback loops.
NOTE: Operational amplfiers are sensitive to output
capacitance and may oscilate. In the event of oscilation,
reduce output capacitance by using shorter cables, or add a
resistor in series with the output.
J4
A voltage divider and filter option (Figure 3) can be added to
establish a power supply-tracking common mode reference
at the VREF input. The inverting and non-inverting inputs
have additional resistor placements for adding input
attenuation, or to establish input DC offsets through the
VREF pin.
DNP
RINA2+
100k
TO INC10
OPEN
TO IN+
J5 OUT
DNP
R27
R25
10k
0
DNP
R26
0
R23
R22
C9
OPEN
C8
C5
+
4.7µF
TO OUT
OPEN
0
R6
R9
R3
DNP
IN2+ J8
DNP
OPEN
RINA+
R11
DNP
10k
C7
RREF
RREFA+
R14
R13
RINA1+
R7
IN1+ J7
0
DNP
R17
OPEN
DNP
RREFAR15
R12
R8
R2
DNP
10k
RINA2-
DNP
R5
IN- J6
0
C6
10k
RINAR10
R18
REF1
RGA+
FIGURE 4. 1/2 OUTPUT STAGE
FIGURE 3. 1/2 INPUT STAGE
ISL281x8EVAL1Z Components Parts List
DEVICE NUMBER
C1, C2, C5
DESCRIPTION
COMMENTS
CAP-TANTALUM,S MD, D, 4.7µF, 50V, 10%, LOW ESR, ROHS
Power Supply Decoupling
C3, C4
CAP, SMD, 0603, 0.1µF, 25V, 10%, X7R, ROHS
Power Supply Decoupling
C6 to C10
CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS
User-selectable capacitors - not
populated
DIODE-RECTIFIER, SMD, SOD-123, 2P, 40V, 0.5A, ROHS
Reverse Power Protection
D1, D2
U1 (ISL28138EVAL1Z)
ISL28138FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS
U1 (ISL28148EVAL1Z)
ISL28148FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS
U1 (ISL28158EVAL1Z)
ISL28158FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS
U1 (ISL28168EVAL1Z)
ISL28168FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS
R2, R3, R6, R8, R9, R12, R13, RESISTOR, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER
R15, R16, R23, R25, R27
User-selectable resistors - not
populated
R1, R10, R11, R17, R20, R21, RES, SMD, 0603, 0Ω, 1/10W, TF, ROHS
R24, R26, R22
0Ω user selectable resistors
R4, R5, R7, R18
RES, SMD, 0603, 10k, 1/10W, 1%, TF, ROHS
Gain and other user selectable
resistors
R14, R19
RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS
Gain resistors
2
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Application Note 1350
ISL281x8EVAL1Z Top View
3
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Application Note 1350
J5
CLOSE TO PART
OUT
ISL281x8EVAL1Z Schematic Diagram
DNP
0
VP
V+
10K
C3
0.1µF
R26
R27
R25
0
J1
4.7µF
R23
C9
0
0
4.7µF
J2
R22
0
R1
R21
C2
D1
DNP
OPEN
C1
R24
D2
OPEN
VM
C8
0
J3
4
SOT23_6
4
5
PACK. 5
3
GENERIC
3
2
2
1
1
U1
100k
R19
6
6
VP
0.1µF
C4
V-
CLOSE TO PART
R20
RREF
4.7µF
VP
C10
J8
IN2+
DISABLE
ENABLE
1
3
10k
2
R4
DNP
RINA2+
R6
OPEN
S1
R11
0
RINA+
C7
10k
R7
RINA1+
J7
IN1+
R5
OPEN
R2
R3
10k
RINA2DNP
DNP
J6
R8
R9
IN-
DNP
DNP
C6
R12
0
OPEN
R14
100k
DNP
R10
R16
RREFA+
DNP
R15
RREFA-
R13
J9
J4
REF1
DNP
EN
DNP
R17
RINA-
DNP
0
10k
R18
RGA+
VM
C5
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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