an1353

ISL28474EVAL1Z Evaluation Board User’s Guide
®
Application Note
August 23, 2007
AN1353.0
The ISL28474EVAL1Z evaluation board is a design platform
containing all the circuitry needed to characterize critical
performance parameters of the ISL28474 instrumentation
and precision operational amplifiers, using a variety of user
defined test circuits.
External power connections are made through the VSP (+V),
VSM (-V) and Ground connections on the evaluation board.
For single supply operation, the VSM and Ground pins are
tied together to the power supply negative terminal. For split
supplies VSP and VSM connect to their respective power
supply terminals. Resistors R3 and R34 are 0Ω but can be
changed by the user to provide power supply filtering, or to
reduce the voltage rate-of-rise to less than ±1V/µs.
Anti-reverse diodes D1, D2 and D3 protect the circuit in the
case of accidental polarity reversal.
C1
+
0 D1 4.7µF
D3
0
R4
CLOSE TO PART
Reference Documents
A
C
NC
MMBZ52XXB
C4
• ISL28274, ISL28474 Data Sheet
0.1µF
C14
Evaluation Board Key Features
0.01µF
0
• ISL28474EVAL1Z
V+
R1
R2
C2
+
4.7µF D2 0
R3
V-
Ordering Information
J2
The ISL28474 is the combination of two micropower
instrumentation amplifiers (Amp A) and two low power
precision amplifiers (Amp B) in a single package. This device
is optimized for 2.4V to 5V single supplies, and can be
operated from one lithium cell or two Ni-Cd batteries.
J1
Power Supplies (Refer to Figure 1)
J3
Introduction
C5
+
DNP
VM
C3 CLOSE TO PART
0.1µF
C18
0.01µF
VP
The ISL28474EVAL1Z is designed to be operated from a
single supply (+2.4VDC to +5VDC), or from split supplies
(±1.2VDC to ±2.5V). Amp A is compensated for a gain of
100, and Amp B is compensated for a gain of 10. Each
precision amplifier contains it’s own VREF input to establish
an input common mode reference. An ENABLE select switch
is provided for each amplifier to be used to save power by
powering the device down.
FIGURE 1. POWER SUPPLY CIRCUIT
Amplifier Configuration (Figures 2 and 3)
The schematic of instrumentation amplifiers (Amp A) is
shown with components supplied in Figure 2, and the
schematic of precision amplifiers (Amp B), is shown with
components supplied in Figure 3.
.
VP
IN+(X)
IN+
IN-
ININ+
IN-(X)
100kΩ
VCM
FB+
FB-
100kΩ
ENABLE
1/2 AMP A
+
V+
-
0Ω
VOUT(x)
V-
+
-
10kΩ
VREF (X)
GND
VREF
Rg
RF
1kΩ
100kΩ
VM
FIGURE 2. BASIC INSTRUMENTATION AMPLIFIER CIRCUIT
1
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 registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2007. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note 1353
.
RF
1/2 AMP B
100kΩ
IN-(X)
RIN-
VP
IN-
IN-
IN+
V+
RIN+
V-
IN+
IN+(X)
VREF (X)
0Ω
VOUT(x)
VM
10kΩ
RREF = (X)
100kΩ
0Ω
10kΩ
GND
0Ω
+
10kΩ
VCM
VREF
-
10kΩ
TO OTHER CHANNEL
FIGURE 3. BASIC PRECISION AMPLIFIER CIRCUIT
User-selectable Options (Figures 4 and 5)
FB+A
J6
DNP
R27
DNP
R9
R28
0
1K
DNP
R23
DNP
R24
IN+A
100K
0
IA FB+ 1
IA FB- 1
IA IN- 1
IA IN+ 1
R14
J8
R19
100K
0
AMP A
IN+ 1
IN+B
OPEN
R16
J9
IN- 1
100K
R29
C7
OUT 1
10K
DNP
R21
C13
OPEN
R34
C8
100K
OPEN
R17
J10
DNP
R22
R11
10K
DNP
IN-B
DNP
R30
0
OPEN
10k
OPEN DNP
OUT
0
IA OUT-1
OPEN
R31
R13
J7
100K
C12
R18
IN-A
DNP
R36
DNP
A voltage divider and filter option (Figure 5) can be added to
establish a power supply tracking common mode reference
at the VREF input. The differential inputs have additional
resistor placements for adding input attenuation, or to
establish input DC offsets through the VREF pin (AMP B).
For Amp A (Figure 5, Top), a coaxial connection to the
amplifier FB+ pin can be made at the FB+ BNC connector.
For Amp B (Figure 5, Bottom), the additional unpopulated
components allow the user to configure the board for a
variety of other applications such as cascaded gain stages,
active feedback loops, etc.
VREF
R8
R10
Component pads are included to enable a variety of
user-selectable circuits to be added to the amplifier
differential inputs, the VREF input, outputs and the amplifier
feedback loop. The outputs (Figure 4) have additional
resistor and capacitor placements for loading.
AMP B
FIGURE 4. OUTPUT STAGE
2
FIGURE 5. 1/2 AMPLIFIER INPUT CIRCUIT
AN1353.0
August 23, 2007
Application Note 1353
ISL28474EVAL1Z Components Parts List
DEVICE NUMBER
DESCRIPTION
COMMENTS
C1, C2, C6
CAP, SMD, 1206, 4.7µF, 25V, 10%, X7R, ROHS
Power Supply Decoupling
C3, C4, C23
CAP, SMD, 0805, 0.1µF, 25V, 10%, X7R, ROHS
Power Supply Decoupling
C14, C18
CAP, SMD, 0805, 0.01µF, 25V, 10%, X7R, ROHS
Power Supply Decoupling
C7 -C13, C15 -C17, C19 -C22
CAP, SMD, 0805, DNP-PLACE HOLDER, ROHS
Optional Caps Not Populated
C5
CAP-TANTALUM, SMD, D, 10µF, 35V, 10%, LOW ESR, ROHS Optional Filter Not Populated
D1, D2, D3
DIODE-RECTIFIER, SMD, ROHS
U1
Reverse Power Protection
ISL28474FAZ INSTRUMENTATION AMP/PRECISION AMP
COMBINATION ,24P, QSOP, ROHS
R8, R10, R11, R18, R20- R23, R27, R30, R32, RES, SMD, 0805, DNP-PLACE HOLDER, ROHS
R35- R37, R39- R42, R47, R48, R51, R54- R56,
R58, R66, R68, R69
User Selectable Resistors
Not Populated
R1- R5,R7, R9, R13, R14, R25, R26, R53, R57, RES, SMD, 0805, 0W, 1/8W, TF, ROHS
R64, R65, R67, R70
0W User Selectable Resistors
R28, R49
RES, SMD, 0805, 1k, 1/8W, 1%,TF, ROHS
User Selectable Resistors
R6, R12, R15- R17, R33, R38, R44, R45, R60,
R63
RES, SMD, 0805, 10k, 1/8W, 1%,TF, ROHS
User Selectable Resistors
R19, R24, R29, R31, R34, R43, R46, R50, R52, RES, SMD, 0805, 100k, 1/10W, 1%, TF, ROHS
R59
S1-S4
User Selectable Resistors
SWITCH-SEALED MINI TOGGLE, TH, 3P, SP, ON/NONE/ON, Enable/Disable Select Switches
GOLD
3
AN1353.0
August 23, 2007
Application Note 1353
ISL28474EVAL1Z Top View
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
4
AN1353.0
August 23, 2007
ISL28474EVAL1Z Schematic Diagram
OUT A
FB+A
IN-A
J5
J6
J7
J8
J9
R8
DNP
R9
0
R13
0
R14
0
R18
C7
OPEN
R16
10K
C8
10K
OPEN
R17
REF1
0
R28
1K
RREF
ENABLE A
C13
8
C2
U1
4.7UF
VM
IA OUT-1
D2
0
R2
IA OUT-2
M24.15
13
14
15
16
17
18
A
NC
0
R1
D3
C
MMBZ52XXB
OUT 2
NC
IN- 2
IN+ 2
EN 2
19 IA EN 2
20 IA IN+ 2
21 IA IN- 2
22 IA FB- 2
23 IA FB+ 2
24
S3
D1
Application Note 1353
V-
EN 1
9
OUT 1 12
NC 11
IN- 1 10
IN+ 1
7
IA EN 1 6
IA IN+ 1 5
IA IN- 1 4
IA FB- 1 3
IA FB+ 1 2
1
0.01UF
C14
0.1UF
C4
CLOSE TO PART
R36
DNP
VP
OPEN
R34
S1
100K
J12
H
2
J2
2
2
VM
3
S4
VM
J14
H
C1
4.7UF
C5
DNP
R42
DNP
C16
V+
C3
C18
0.1UF
0.01UF
ENABLE D
VP
ENABLE D
10K
R45
VP
J15
OPEN
R43
1
3
100K
H
L
VP
ENABLE C
10K
R44
1K
R49
VREF
CLOSE TO PART
R47
VREF
0
R26
VREF
R25
3
L
2
0
R53
0
R57
10K
OPEN
R61
C22
10K
OPEN
R60
C21
DNP
0.1UF
R33
1
VM
S2
100K
R3
C17
R5
J1
0
OPEN
R46
ENABLE C
R58
OPEN
1
DNP
C15
DNP
L
R66
0
R67
0
R64
0
R65
0
R70
DNP
100K
OPEN
10K
L
DNP
R51
C23
DNP
ENABLE A
3
ENABLE B
R38
H
J13
R37
1
R68
R52
C11
VP
10K
DNP
R41
DNP
10K
R69
IN+A
IN+B
R7
R31
VP
OPEN
ENABLE B
VM
DNP
4.7UF
DNP
0
DNP
R63
10K
J22
J21
J20
J19
J18
J17
3
4
J16
3
4
5
5
5
OUT D
FB+D
IN-D
IN+D
IN+C
IN-C
OUT C
AN1353.0
August 23, 2007
3
4
J10
J11
0
C6
J4
R6
10K
R30
J3
VM
R39
R4
R35
R32
100K
C12
DNP
100K
OPEN
DNP
R48
R50
C19
100K
DNP
DNP
DNP
R62
IN-B
OUT B
0
5
R40
R59
OPEN
R54
R55
R56
C20
DNP
100K
DNP
DNP
100K
OPEN
R23
R27
R29
C10
R24
DNP
DNP
R20
DNP
DNP
100K
R21
R22
C9
OPEN
10K
R10
DNP
R19
10K
R12
R11
R15
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