AN1653 Просмотр технического описания (PDF) - Intersil
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AN1653 Datasheet PDF : 5 Pages
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Application Note 1653
ISL70218SRH Evaluation Board User’s Guide
Introduction
The ISL70218SRHMEVAL1Z evaluation board is designed to
evaluate the performance of the rad hard ISL70218 40V
Precision Low Power Operational Amplifier. The ISL70218 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 ISL70218 can operate from a
single or dual supply with a 3V to 40V supply range. The
ISL70218 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.
Reference Documents
• ISL70218 Data Sheet, FN7871
Evaluation Board Key Features
• Single Supply Operation: +3V to +40V
• Dual Supply Operation: +1.8V/-1.2V to ±20V
• Singled-Ended or Differential Input Operation
• 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.
J5
V- J6
J7
V+ J8
VREF
J9
J10
C2
C4
1µF
1µF
D1
C3
C6
0.1µF
C5
0.1µF
C7
0.01µF
0.01µF
FIGURE 1. POWER SUPPLY CIRCUIT
Amplifier Configuration
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:
VOUT = (VIN+ – VIN- ) • (RF ⁄ RIN ) + VREF
(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 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. 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.
July 7, 2011
1
AN1653.0
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
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