Renesas Intersil ISL28133EVAL1Z User manual

USER’S MANUAL
AN1499
Rev.0.00
Oct 2, 2009
ISL28133EVAL1Z
High Gain Evaluation Board User Guide
AN1499 Rev.0.00 Page 1 of 4
Oct 2, 2009
Introduction
The maximum useful signal range of a high gain DC
amplifier is limited by the amplifiers own DC offset and
low frequency noise. For battery powered amplifiers
the problem is further compounded due to limits of low
battery voltage. For example, the useful input voltage
range of an ideal amplifier with 10kV/V gain operating
from a 3V Lithium cell would be 300µV, which would
drive the to the maximum possible +3V output. A
standard low offset amplifier with 100µV VOS would
reduce the maximum useful input voltage range from
300µV to 200µV, since the input offset voltage alone
would drive the amplifier output to 10k times that,
taking up 1V of the 3V total available voltage range.
Further reductions due to offset voltage drift, low
frequency 1/f noise, and the inability to swing the
output close to the power supply rails can limit the best
amplifiers to DC gains no higher than several hundred
V/V.
The ISL28133 chopper stabilized rail-to-rail op amp
features a low 8µV maximum VOS over-temperature
and a 0.1Hz 1/f noise corner frequency enabling very
high gain single-stage DC amplifiers that can operate
from single cell batteries while consuming only 20µA of
current. The ISL28133EVAL1Z evaluation board is
configured as a precision high-gain (G = 10,000)
differential amplifier and demonstrates the level of
performance possible with this type of amplifier while
operating from battery voltages as low as 2.4V.
Reference Documents
• Data Sheet (ISL28133)
Evaluation Board Key Features
The ISL28133EVAL1Z 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
single-ended or differential input with a closed loop
gain of 10,000. A single external reference voltage
(VREF) pin and provisions for a user-selectable voltage
divider-filter are included.
Power Supplies (Figure 2)
External power connections are made through the V+,
V-, VREF, 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 supply terminals. De-
coupling capacitors C2 and C4 provide low-frequency
power-supply filtering, while four additional capacitors,
C1, C5, C7 and C8, which are connected close to the
part, filter out high frequency noise. Anti-reverse
diodes D1 and D2 (optional) protect the circuit in the
case of accidental polarity reversal.
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.
IN-
IN+
RF
VREF
IN -
IN +
GND
1M
RG
OPEN
VOUT
ISL28133
VP
V-
0
VM
VCM
IN-
IN+
VREF
V+
RIN-
100
RIN+
100
-
+
01M
RL
OPEN
FIGURE 1. BASIC AMPLIFIER CONFIGURATION

AN1499 Rev.0.00 Page 2 of 4
Oct 2, 2009
ISL28133EVAL1Z
Amplifier Configuration
(Figure 2)
The schematic of the op amp with the components
supplied is shown in Figure 2, with a closed loop gain of
10,000. The circuit implements a Hi-Z differential input
with unbalanced common mode impedance. The
differential amplifier gain is expressed in Equation 1:
where: RF = RGand RIN+ = RIN- and the differential
input impedance is ~1M with VREF at GND. The IN- input
connects to the amplifier summing junction and it’s
impedance to ground is a low 100  The impedance of the
IN+ input to ground is much higher at 1.001M
 to VREF.
For single-ended input inverting operation (G = -10001),
the IN+ input is grounded and the signal is supplied to
the IN- input. VREF must be connected to a reference
voltage between the V+ and V- supply rails. For
non-inverting operation (G = 10,000), the IN- input is
grounded and the signal is supplied to the IN+ input. The
non-inverting gain is strongly dependent on any
resistance from IN- to GND. For good gain accuracy, a 0
resistor should be installed on the empty R7 pads.
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
inputs, the VREF input, outputs and the amplifier
feedback loops.
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.
The output (Figure 4) also has additional resistor and
capacitor placements for filtering and loading.
NOTE: Operational amplifiers are sensitive 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.
R4
D2D1
R16
C2 C4
J8
J11
J9 J10
J7 J13
DNP
DNP
S1AB
1µF 1µF
S1AB
VREF
V+
V-
0.1µF
C7 C1
0.01µF
0.1µF
C8 C5
0.01µF
FIGURE 2. POWER SUPPLY CIRCUIT
VOUT VIN+ VIN-RF  RIN–VREF += (EQ. 1)
IN +
IN -
DNP
R7
R5
J2
J1 R1
R2
R12
R15
R13
R11R9
10k
DNP
DNP
0
10k
DNP
100k
OPEN
100k
VREF
TO IN -
TO IN +
FROM OUT
FIGURE 3. INPUT STAGE
OUTPUT
R18
J12
C6
R17
DNP
OPEN
0
FIGURE 4. OUTPUT STAGE
TABLE 1. ISL28133EVAL1Z COMPONENTS PARTS LIST
DEVICE # DESCRIPTION COMMENTS
C2, C4 CAP, SMD, 0603, 1µF, 25V, 10%, X7R, ROHS Power Supply Decoupling
C1, C5 CAP, SMD, 0603, 0.1µF, 25V, 10%, X7R, ROHS Power Supply Decoupling
C7, C8 CAP, SMD, 0603, 0.01µF, 25V, 10%, X7R , ROHS Power Supply Decoupling
C3, C6 CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS User selectable capacitors - not populated
D1, D2 DIODE-RECTIFIER, SMD, SOD-123, 2P, 40V, 0.5A, ROHS Reverse Power Protection
U1 (ISL28133EVAL1Z) ISL28133FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS
R1-R4, R6-R8, R10, R13,
R14, R16, R17, R19, R21 RESISTOR, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER User selectable resistors - not populated
R5, R18 RES, SMD, 0603, 0, 1/10W, TF, ROHS 0user selectable resistors
R9, R12 RES, SMD, 0603, 100, 1/10W, 1%, TF, ROHS Gain resistors
R11, R15 RES, SMD, 0603, 1M, 1/10W, 1%, TF, ROHS Gain resistors

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 document is current before proceeding.
For information regarding Intersil Corporation and its products, see www.intersil.com
ISL28133EVAL1Z
AN1499 Rev.0.00 Page 3 of 4
Oct 2, 2009
© Copyright Intersil Americas LLC 2009. All Rights Reserved.
All trademarks and registered trademarks are the property of their respective owners.
ISL28133EVAL1Z Top View

AN1499 Rev.0.00 Page 4 of 4 Oct 2, 2009
ISL28133EVAL1Z
ISL28133EVAL1Z Schematic Diagram
IN- OUT
OUTPUT
IN +
IN -
IN+ NODE
ENABLE
R4
0.1µF
C7 C1
0.01µF
C5
0.01µF
C8
0.1µF
DNP
U1
J14
R19
R21
R20
1
3
2
S1
D2D1
R18
R16
J4 J6 J5 J3
C3
R7
R5
C2 C4
J12
J2
J1
J8
J11
J9
J10
J7
J13
C6
R1
R6
R14
R2
R17
R12
R3
R15R13
R10R8
R11R9
DNP
DNP
100
DNP DNP
DNP
DNP DNP
DNP
0
S1AB
1µF
DNP
100
DNP
DNP
OPEN
0
1µF
S1AB
DNP
SOT23_6
1M
OPEN
1M
VREF
VREF
V+V-
4
6
3
25
1
GENERIC
PACK.
DNP
DNP