Intersil ISL28470EVAL1Z User Manual

®

ISL28470EVAL1Z Evaluation

Board User’s Guide

Application Note February 12, 2007

Introduction

The ISL28470EVAL1Z evaluation board is a design platform
containing all the circuitry needed to characterize critical
performance parameters of the ISL28470 Quad
Instrumentation Amplifier using a variety of user defined test
circuits.

The ISL28470 is a quad channel instrumentation amplifier
optimized for 2.4V to 5V single supplies. The device features
an Input Range Enhancement Circuit (IREC) which
maintains CMRR performance for input voltages equal to the
positive supply and down to 50mV above the negative
supply rail. The input signal is capable of swinging above the
positive supply rail and to the negative supply with only a
slight degradation of the CMRR performance. The output
operation is rail to rail. The ISL28270 is compensated for a
minimum gain of 100.

Reference Documents

• ISL28470 Data Sheet, FN6260

Evaluation Board Key Features

The ISL28470EVAL1Z 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 4
independent instrumentation amplifiers connected for a
closed loop gain of 101 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
provided for each amplifier to be used to save power by
powering the device down.

select switch is

AN1289.0

GND V-V+

VP

J

3

V+

R

C

2

++

11

0

4

22

R

D

2

C

9

11

0.1µF 0.1µF

J

2

R

2

22

1

004.7µF 4.7µF

C

D

1

C

10

J

1

V-

1

R

0

3

VM

FIGURE 1. POWER SUPPLY CIRCUIT

Power Supplies (Refer to Figure 1)

External power connections are made through the +V, -V
and 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
and -V terminals connect to their respective power supply
terminals. De-coupling capacitors, C
ground through R
R

are 0Ω but can be changed by the user to provide power

4

and R2, 0Ω resistors. Resistors R3 and

1

supply filtering, or to reduce the voltage rate-of-rise to less
than ±1V/µs. Anti-reverse diodes D
circuit in the case of accidental polarity reversal.

and C2, connect to

1

and D2 protect the

1

IN+(x)

IN+

IN-

IN-(x)

VCM

VREF(x)

VREF

GND

1

VP

ENABLE

IN+

+

IN-

-

100kΩ

100kΩ

R

1kΩ

FB+

+

FB-

-

G

R

F

100kΩ

-V

VM

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 registered trademark of Intersil Americas Inc.

All other trademarks mentioned are the property of their respective owners.

1/4 ISL28470

0Ω

10kΩ

Copyright Intersil Americas Inc. 2007. All Rights Reserved

VOUT(x)

Application Note 1289

Amplifier Configuration (Figure 2)

The schematic of each of the 4 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. 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.

User-selectable Options (Figure 3)

Component pads are included to enable a variety of user­selectable 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 ISL28470 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.

ISL28470EVAL1Z Components Parts List

VREFA

J

4

1

FB+A

-INA

+INA

R

J

R

8

13

DNP

J

R

9

18

0

R

19

DNP

J

R

10

21

0

R

22

DNP

R

6

C

R

3

14

0

R
100k

DNPDNP

OPEN

VREFA

20

100k

5

VREFA

R

23

V+V-

R

15

DNP

R

17

1k

R

16

DNP

FIGURE 3. COMPONENT-SELECTABLE OPTIONS

DEVICE # DESCRIPTION COMMENTS

C

, C

1

C

, C

7

C9, C
C

3-C6

C

11-C18

D

, D

1

2
8
10

2

CAP-TANTALUM, SMD, D,4.7µF, 50V, 10%, LOW ESR, ROHS Power Supply Decoupling
CAP, SMD, 0603, 0.01µF, 25V, 10%, X7R, ROHS Power Supply Decoupling
CAP, SMD, 0805, 0.1µF, 25V,10%, X7R, ROHS Power Supply Decoupling
CAP, SMD, 0805, DNP-PLACE HOLDER, ROHS Optional VREF Filter

CAP, SMD, 0805, DNP-PLACE HOLDER, ROHS Optional Amplifier Feedback Caps

DIODE-RECTIFIER, SMD, MELF, 2 Ld, 50V, 1A, GPP, ROHS Reverse Power Protection

U1 ISL28470FAZIC INSTRUMENTATION AMP, 28P, QSOP,

ROHS

R

, R14-R16, R19, R22, R24-R27, R30, R33,

13

R

35-R38,R41

R

, R73, R

71

, R21, R29, R32, R40, R43, R51, R54, R58,

R

18

R

, R63, R

60

R

, R28, R39, R

17

R

, R61, R65, R67, R70, R72, R74, R

59

, R23, R31, R34, R42, R45, R53, R56, R57,

R

20

R

, R64, R

62

R

1-R4

R

5-R12

S

1-S4

, R44, R46-R49, R52, R55, R69,

75

66

50

68

76

RESISTOR, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER User Selectable Resistors

RES, SMD, 0603, 0Ω, 1/16W, TF, ROHS 0Ω User Selectable Resistors

RES, SMD, 0603, 1k, 1/10W, 1%, TF, ROHS RG Gain Resistors
RES, SMD, 0603, 10k, 1/10W, 1%, TF, ROHS
RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS RF Gain Resistors

RES, SMD, 0805, 0Ω, 1/8W, TF, ROHS 0Ω User Selectable Resistors
RES, SMD, 0805, DNP-PLACE HOLDER, ROHS User Selectable Resistors

SWITCH-SEALED MINI TOGGLE, TH, 3P, SP, ON/NONE/ON,
GOLD

Not Populated

Not Populated

Not Populated

Not Populated
Enable/Disable Select Switches

2

AN1289.0

February 12, 2007