an1290

ISL2827xINEVAL1Z Evaluation Board
User’s Guide
Application Note
June 15, 2009
Introduction
GND
1
2
2
C3
R32
D2
1
2
D1
1
D3
0
1 A
2 NC
1
0.1µF
The ISL2827x series of amplifiers are dual channel
instrumentation amplifiers optimized for 2.4V to 5V single
supplies. These devices feature an Input Range
Enhancement Circuit (IREC) which enables the inputs to
swing to the rails. The ISL28270 and ISL28273 maintain
CMRR performance from the positive rail down to within
50mV of the negative rail. The ISL28271 and ISL28272 can
swing 100mV beyond the rails. The output operation of all
devices is rail-to-rail. The ISL28270 and ISL28272 are
compensated for a minimum gain of 100 and the ISL28271
and ISL28273 are compensated for a minimum gain of 10.
VSP
1
VSM
The ISL2827xINEVAL1Z evaluation board is a design
platform containing all the circuitry needed to characterize
critical performance parameters of the ISL28270, ISL28271,
ISL28272 or ISL28273 Dual Instrumentation Amplifiers using
a variety of user defined test circuits.
AN1290.2
1
®
R33
C 3
2
VM
0
2
C4
1
0.1µF
1
10µF
C5
VP
FIGURE 1. POWER SUPPLY CIRCUIT
Power Supplies (Refer to Figure 1)
• ISL28271, ISL28272 Data Sheet, FN6390
External power connections are made through the VSP (+V),
VSM (-V) and GND connections on the evaluation board.
For single supply operation, the VSM (-V) and GND pins are
tied together to the power supply negative terminal. For split
supplies, VSP (+V) and VSM (-V) terminals connect to their
respective power supply terminals. Resistors R32 and R33
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 and D2 protect the
circuit in the case of accidental polarity reversal.
Evaluation Board Key Features
Amplifier Configuration (Refer to Figure 2)
The ISL2827xINEVAL1Z is designed to be operated from a
single supply (+2.4VDC to +5VDC), or from split supplies
(±1.2VDC to ±2/5V). The board is configured for 2
independent instrumentation amplifiers connected for a
closed loop gain of 101 (ISL28270, ISL28272) or a gain of
10 (ISL28271, ISL28273) with inverting and non-inverting
high impedance terminated with 100k resistors to ground.
Each 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.
The schematic of each of the two op amps with the
components supplied is shown in Figure 2. The circuit
implements a differential input instrumentation amp with a
closed loop gain of 101 for the ISL28270 and ISL28272, and
10 for the ISL28271, ISL28273. The circuit can operate from
a single 2.4VDC to +5VDC supply, or from dual supplies
from ±1.2VDC to ±2.5VDC.The output common mode
reference is applied to the VREF pin, and has a range from
ground (VM) to VP.
Reference Documents
• ISL28270, ISL28273 Data Sheet, FN6260
VP
ENABLE
IN+(x)
IN+
IN+
1/2 ISL28270, ISL28271, ISL28272, ISL28273
+
IN-
IN-
0Ω
VOUT(x)
100kΩ
IN-(x)
FB+
+
-V
VCM
FB-
10kΩ
100kΩ
VREF(x)
RG
1kΩ
VREF
GND
RF
VM
100kΩ (ISL28270, ISL28272)
9.09kΩ (ISL28271, ISL28273)
FIGURE 2. BASIC AMPLIFIER CONFIGURATION
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Copyright Intersil Americas Inc. 2007, 2009. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note 1290
User-selectable Options (Refer to Figure 3)
VREFA
Component pads are included to enable a variety of user
selectable circuits to be added to the amplifier differential
inputs, the VREF input, and the amplifier feedback loop. A
voltage divider and filter option can be added to establish a
power supply tracking common mode reference at the VREF
input, or a coaxial connection to the amplifier FB+ pin can be
made at the FB+ BNC connector. The differential inputs have
additional resistor placements for adding input attenuation,
or to establish input DC offsets through the VREF pin.
V-
1
J4
R6
DNP
R5
V+
DNP
VREFA
C3
J8
FB+A
J9
R18
J10
0
R19
DNP
R21
+INA
R15
R13
DNP
-INA
OPEN
0
R22
DNP
R14
0
VREFA
DNP
R17
R16
DNP
1k
R20
100k
R23
100k
FIGURE 3. COMPONENT-SELECTABLE OPTIONS
ISL2827xINEVAL1Z Components Parts List
DEVICE #
DESCRIPTION
COMMENTS
C3, C5
CAP, SMD, 0805, 0.1µF, 25V, 10%, X7R, ROHS
Power Supply Decoupling
CFA, CFB, CLA, CLB
CAP, SMD, 0805, DNP-PLACE HOLDER, ROHS
Optional Amplifier Feedback Caps
Not Populated
C1, C2
CAP, SMD, 1206, 1µF, 25V, 10%, X7R, ROHS
Power Supply Decoupling
C4
CAP-TANTALUM, SMD, D, 10µF, 35V, 10%, LOW ESR,
ROHS
Optional VREF Filter
Not Populated
D1, D2
DIODE-RECTIFIER, SMD, MELF, 2 Ld, 50V, 1A, GPP,
ROHS
Reverse Power Protection
U1
ISL28270FAZ or ISL28271FAZ or ISL28272FAZ or
ISL28273FAZ INSTRUMENTATION AMP,16P, QSOP,
ROHS
R32, R33, RIN+A, RIN+B, RIN-A, RIN-B, RSA, RSB RES, SMD, 0805, 0Ω, 1/8W, TF, ROHS
0Ω User Selectable Resistors
RIA, RIB.
RES, SMD, 0805, 1k, 1/8W, 1%,TF, ROHS
RI Gain Resistors
R1, R2
RES, SMD, 0805, 10k, 1/8W, 1%,TF, ROHS
ENABLE Pull-up Resistors
R15 to R18
RES, SMD, 0805, 100k, 1/10W, 1%, TF, ROHS
R9, R12, R20, R22, R27, R29
CAP, SMD, 0805, DNP-PLACE HOLDER, ROHS
User Selectable Resistors
Not Populated
RFA, RFB (ISL28271, ISL28273)
RES, SMD, 0805, 9.09k, 1/8W, 1%, TF, ROHS
RF Gain Resistors - ISL28271,
ISL28272
RFA, RFB (ISL28270, ISL28272)
RES, SMD, 0805, 100k, 1/8W, 1%, TF, ROHS
RF Gain Resistors - ISL28270
R3, R6, R10, R11, R13, R14, R19, R21, R23, R25, RES, SMD, 0805, DNP-PLACE HOLDER, ROHS
R28, R30, RLA, RLB, RX.
User Selectable Resistors
Not Populated
S1, S2
Enable/Disable Select Switches
SWITCH-SEALED MINI TOGGLE, TH, 3P, SP,
ON/NONE/ON, GOLD
2
AN1290.2
June 15, 2009
Application Note 1290
ISL2827xINEVAL1Z 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
3
AN1290.2
June 15, 2009
R20
R27
4.7K
4.7K
2
D2
VSP
1
GND
1
VP
1
2
D1
1
0
0
2
2
C5
1
CLOSE TO PART
0.1UF
C4
1
10UF
VP
R21
RSA
0
VP
2
CLA 1
OPEN
1
1
16
16
2
2
15
15
3
14
5
U1
QSOP16 14
Generic
4
13
Pack.
5
12
6
6
11
11
7
7
10
10
1
10K
S2
3
2
2
DISABLE
VM
8
3
8
9
VM
12
1
100K
CFB
2
RSB
OPEN
CLB 1
1
2
VP
4.7K
1UF
C2
1
DNP
RIN-B
0
R23
R30
0
100K
RIB
R18
DNP
2
RIN+B
R13
5
4
3
1
100
DNP
0
+INB
5
2
2
100K
1
5
R17
-INB
4
3
R29
VOUTB
1
2
0
9
DNP
DNP
2
R22
4.7K
R12
5
R6
R14
1
4
3
FB+B
3
4
RFB
13
VREFB
R19
5
4
3
1
ENABLE
VP
1
10K
ENB
4
DISABLE
DNP
R2
ENABLE
3
4
3
2
R25
2
DNP
R1
4
3
5
S1
DNP
1
2
ENA
RLB
1
OPEN
100K
CFA
5
OPEN
RFA
100
RLA
DNP
RIA
VOUTA
1
2
0
RX
DRAWN BY:
ALAN ERZINGER
RELEASED BY:
DATE:
07/25/06
DATE:
UPDATED
DATE:
BY:
ENGINEER:
ROBERT POSPISIL
TITLE:
ISL2827XINEVAL1Z
DATE:
DNP
TESTER
MASK#
AN1290.2
June 15, 2009
FILENAME:
HRDWR ID
SHEET
1
Application Note 1290
R16
2
100K
0
R10
4
3
5
R28
RIN+A
1
DNP
+INA
DNP
R15
100K
0
DNP
2
A
C
3
NC
MMBZ52XXB
RIN-A
R11
5
4
3
1
1
2
VM
4
-INA
1
D3
R33
C1
1UF
C3
0.1UF
DNP
2
R9
4
3
2
2
1
5
CLOSE TO PART
R3
DNP
FB+A
R32
1
VM
1
1 VREFA
VSM
ISL2827xINEVAL1Z Schematic Diagram
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