an1669

Application Note 1669
ISL70227SRH Evaluation Board User’s Guide
C4
1µF
J9
VREF
J10
100
100
R11
C2
1µF
D1
C5
Evaluation Board Key Features
V+ J8
J6
0.1µF
• ISL70227SRH Data Sheet, FN7925
0.01µF
C6
0.1µF
C7
0.01µF
FIGURE 1. POWER SUPPLY CIRCUIT
• Wide Supply Operation: 4.5V to 36V
• Single-Ended or Differential Input Operation
Amplifier Configuration
• External VREF Input
• Banana Jack Connectors for Power Supply and VREF Inputs
• BNC Connectors for Op Amp Input and Output Terminals
• Convenient PCB Pads for Op Amp Input/Output Impedance
Loading
Power Supplies
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 power supply
terminals. De-coupling capacitors C2, C3, C4 and C6 connect
to their respective supplies through R11 and R15 resistors.
These resistors are 100Ω but can be changed by the user to
provide additional power supply filtering, or to reduce the
voltage rate-of-rise to less than ±1V/µs. Two additional
capacitors, C5 and C7, are connected close to the part to filter
out high frequency noise. Anti-reverse diode D1 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.
1
V-
C3
Reference Documents
September 23, 2011
AN1669.0
J7
J5
The ISL70227MHEVAL1Z evaluation board is designed to
evaluate the performance of the rad hard ISL70227SRH 36V
Precision Low Power Operational Amplifier. The ISL70227SRH
can operate from a dual supply with a 4.5V to 36V supply
range. The ISL70227SRH features very low power, low offset
voltage and low temperature drift, making it ideal for
applications for precision instrumentation, current sensing and
power supply, and industrial process controls.
R15
Introduction
A simplified schematic of the evaluation board is shown in
Figure 2. The 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:
V OUT = ( V IN+ – V IN- ) • ( R F ⁄ R IN ) + V REF
(EQ. 1)
For single-ended input with an inverting gain G = -10V/V, the
IN+ input is grounded and the signal is supplied to the INinput. 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. The VREF
pin must be connected to ground to establish a ground
referenced input for dual supply operation, or can be externally
set to any reference level for single supply operation. VREF
should not be left floating.
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas Inc. 2011. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
Application Note 1669
RF
ISL70227(1/2)
100kΩ
IN -
VP
RIN-
IN-
IN-
-
RIN+
IN+
IN+
10kΩ
IN +
0Ω
V+
10kΩ
VOUT
V+
VN
VCM
VREF
RREF+
RL
100kΩ
DNP
GND
VREF
FIGURE 2. BASIC AMPLIFIER CONFIGURATION
100k
C1
J2
R10
R2
OPEN
VREF
10k
DNP
R6
R12
DNP
100k
OUTPUT
ININ+
FIGURE 3. INPUT STAGE (1/2)
FROM OUTPUT
C6
OPEN
R26
0
DNP
R9
10k
OPEN
R28
R4
0
C8
DNP
R3
R5
R1
DNP
J1
FIGURE 4. OUTPUT STAGE (1/2)
User-selectable Options
Component pads are included to enable a variety of
user-selectable circuits to be added to the amplifier VREF,
inputs, outputs, and the amplifier feedback loops.
A voltage divider (Figure 3, R6 and R12) can be added to
establish a power supply-tracking common mode reference
using the VREF input. The input stages (see Figure 3) have
additional resistor and/or capacitor pads that may be used to
add voltage divider networks or feedback networks for adding
input attenuation, or to establish input DC offsets through the
VREF pin. The output stages (see Figure 4) have additional
resistor and capacitor placements for 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.
2
AN1669.0
September 23, 2011
Application Note 1669
TABLE 1. ISL70227MHEVAL1Z COMPONENTS PARTS LIST
DEVICE #
DESCRIPTION
COMMENTS
C2, C4
CAP, SMD, 1210, 1µF, 50V, 10%, X7R, ROHS
Power Supply Decoupling
C3, C6
CAP, SMD, 0805, 0.1µF, 50V, 10%, X7R, ROHS
Power Supply Decoupling
C5, C7
CAP, SMD, 0603, 0.01µF, 50V, 10%, X7R, ROHS
Power Supply Decoupling
C1, C8-C12
CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS
User selectable capacitors - not populated
D1
DIODE-RECTIFIER, SMD, SOD-123, 2P, 40V, 0.5A, ROHS
Reverse Power Protection
U1
ISL70227SRHM, DUAL OP-AMP, 10 Ld. FLATPAK
R1, R2, R5-R8, R14, R20, R23, R24,
RESISTOR, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER
User selectable resistors - not populated
R3, R20-R22
RES, SMD, 0603, 0Ω, 1/10W, TF, ROHS
Zero ohm resistors
R4, R10, R17, R18
RES, SMD, 0603, 10k, 1/10W, 1%, TF, ROHS
Gain resistors
R10, R12, R13, R16
RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS
Gain resistors
3
AN1669.0
September 23, 2011
Application Note 1669
FIGURE 5. ISL70227MHEVAL1Z 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
AN1669.0
September 23, 2011
5
Application Note 1669
FIGURE 6. ISL70227MHEVAL1Z SCHEMATIC DIAGRAM
AN1669.0
September 23, 2011
Similar pages