an1595

Application Note 1595
ISL28218SOICEVAL1Z Evaluation Board User’s Guide
Introduction
Power Supplies (Figure 1)
The ISL28218SOICEVAL1Z evaluation board is designed to
evaluate the performance of the ISL28218 40V Precision
Low Power Operational Amplifier. The ISL28218 is a single
supply rail-to-rail output, dual amplifier with ground sensing
inputs that allow the common mode input voltage to swing
0.5V below the V- rail. The ISL28218 can operate from a
single or dual supply with a 3V to 40V supply range. The
ISL28218 features very low power, low offset voltage and
low temperature drift making them ideal for applications for
precision medical and instrumentation, current sensing and
power supply and industrial process controls.
External power connections are made through the V+,
V-, VREF, and GND connections on the evaluation board.
The circuit can operate from a single supply or from dual
supplies. For single supply operation, the V- and GND
pins are tied together to the negative or ground
reference of the power supply. 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 additional capacitors, C3
and C5, which are connected close to the part, filter out
high frequency noise. Anti-reverse diode D1 (optional)
protects the circuit in the momentary case of accidentally
reversing the power supplies to the evaluation board.
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.
C4
1µF
1µF
1
2
• Convenient PCB pads for Op Amp Input/Output
impedance loading.
1
1
0
1 R16 2 1
C2
3
• BNC Connectors for Op Amp Input and Output
Terminals
VREF
J14
• Banana Jack Connectors for Power Supply and VREF
Inputs
3
2
J13
3
2
• External VREF input
V+
J8
V-
• Singled-Ended or Differential Input Operation
J12
• Dual Supply Operation: ±1.5V to ±20V
1
J6
J11
• Single Supply Operation: +3V to +40V
0
Evaluation Board Key Features
1 R31 2 1
• ISL28218 Datasheet, FN7532
1
Reference Documents
D1
CLOSE TO DUT
C3
C5
0.01µF 0.01µF
FIGURE 1. POWER SUPPLY CIRCUIT
R13/R23
100kΩ
LOAD
R11/R24
RSENSE
INA- 2
INB- 6
10kΩ
R14/R21
INA+ 3
INB+ 5
8
-
V+
ISL28218
V-
+3V TO 40V
1/7
+
4
10kΩ
VOUT
GAIN = 10V/V
R18/R19
100kΩ
VREF
FIGURE 2. CURRENT SENSE AMPLIFIER
October 27, 2010
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1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Copyright Intersil Americas Inc. 2010. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note 1595
Amplifier Configuration
(Figure 3)
User-selectable Options
(Figures 3 and 4)
The schematic of the op amp input stage with the
components supplied is shown in Figure 3, with a closed
loop gain of 10V/V. The differential amplifier gain is
expressed in Equation 1:
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.
(EQ. 1)
V OUT = ( V IN+ – V IN- ) • ( R F ⁄ R IN ) + V REF
For single-ended input with an inverting gain G = -10V/V,
the IN+ input is grounded and the signal is supplied to the
IN- input. VREF can be connected to a reference voltage
between the V+ and V- supply rails. For non-inverting
operation with G = 11V/V, 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 0Ω resistor should be
installed on the empty R5 pad.
C1
R26
FROM VOUTA
100k
J15
VOUT_A
0
C6
OUT A
DNP
10k
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.
OPEN
R28
0
OPEN
R13
The output (Figure 4) also has additional resistor and
capacitor placements for filtering and loading.
C8
R1
DNP
R11
DNP
R4
J1
R5
IN-A
A voltage divider (Figure 3, R18 and R15) can be added
to establish a power supply-tracking common mode
reference using 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.
OPEN
TO INA R14
IN+A J2
R2
TO INA +
FIGURE 4. OUTPUT STAGE
10k
DNP
R15
R18
DNP
100k
VREF
FIGURE 3. INPUT STAGE
TABLE 1. ISL28218SOICEVAL1Z COMPONENTS PARTS LIST
DEVICE #
DESCRIPTION
COMMENTS
C2, C4
CAP, SMD, 1206, 1µF, 50V, 10%, X7R, ROHS
Power Supply Decoupling
C3, C5
CAP, SMD, 0603, 0.01µF, 50V, 10%, X7R, ROHS
Power Supply Decoupling
CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS
User selectable capacitors - not populated
RESISTOR, SMD, 0603, 10kΩ, 1%, 1/16W, ROHS
Gain Setting Resistor
RESISTOR, SMD, 0603, 100kΩ, 1%, 1/16W, ROHS
Gain Setting Feedback Resistor
C1, C6, C7, C8, C9, C10
R11, R14, R21, R24
R13, R23
R1-R3, R5-R8, R10, R12, RESISTOR, SMD, 0603, DNP-PLACE HOLDER, ROHS
R15, R17, R20, R22, R28R30, R32, R34-R36
D1
U1 (ISL28218FBZ)
40V DUAL SERIES SCHOTTKY BARRIER DIODE
User selectable resistors - not populated
Reverse Power Protection
ISL28218FBZ, IC 40V RAIL-TO-RAIL OP AMP, SOIC, ROHS
2
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Application Note 1595
ISL28218SOICEVAL1Z 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
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ISL28218SOICEVAL1Z Schematic Diagram
J11
J6
J14
3
VREF
J13
3
J12
V+
J8
V-
C4
1
1
0
1
1
R16 2 1
0
1
C2
3
4
1µF
1 R31 2 1
2
2
1µF
1
2
D1
CLOSE TO DUT
C3
C5
0.01µF
R8 2
DNP
3
4
1
OPEN
1 R28 2
DNP
C8
2
J24
0
1
2
OUT B
3
4
1
OPEN
R29
1
2
DNP
2 C7 1
OPEN
1 R27 2
C9
DNP
1 R36 2
DNP
R35
1 R25 2 1
2
0
DNP
1 R20 2
2
DNP
R30
J23
J21
J20
J19
J18
J17
R6 2
DNP
1
2 1
DNP
R5
1
DNP
R3 2
1
4
3
4
3
4
3
4
3
IN+B
1
J4
2
1
5
R7 2
DNP
OPEN
1 R26 2
0
2
1 R15 2 1 R18 2 1 R19 2 1 R22 2
100k
100k
DNP
DNP
1
2 1
1
IN-B
2
R24 2
1 R23 2 1
10k
100k
C10 1
8
2
1
8
U1
OPEN 2
OPEN
2 SOIC8 7 7
1 R14 2 3 3 GENERIC 6 6
PACK.
R21 2
10k
4 4
5 51
10k
R4 2 1 R11 2 1 R13 2
0
10k
100k
2 C1 1 1
IN-
1 R32 2 1 R34 2
DNP
DNP
VREF
J3
5
1
2
DNP
2
R2 2
DNP
R12
1
1
2 1
2 1
2
1
1
J2
5
1 R1 2
DNP
2
IN+A
1
2
R10
DNP
1
J1
5
2
2
2
IN-A
1
1
1
1
OUT NODE IN+
J22
IN+ NODE OUT
1 R17 2
DNP
IN-
OUT A
1
J15
2
5
1
J16
5
Application Note 1595
2 C6
2
0.01µF
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