Application Note 1145
Author: Daniel Goodhew
A Compendium of Application Circuits for Intersil
Digitally-Controlled (XDCP) Potentiometers
Introduction
This application note lists a number of application circuits for
Intersil’s digitally-controlled (XDCP) potentiometers. The
application circuits illustrate the wide variety of possible
functions which can be implemented using the variability of
the potentiometer in conjunction with standard active devices
like operational amplifiers and comparators. The types of
circuits include control circuits, converters, filters, signal
processing circuits, regulators, wave shapers, analog
computing circuits and signal sources. The circuits are shown
in basic form and do not include supply decoupling or proper
grounding techniques. The user must account for these in the
final design.
Electronic digitally-controlled (XDCP) potentiometers provide
three powerful application advantages:
1. The variability and reliability of a solid-state potentiometer.
2. The flexibility of computer-based digital controls.
3. The retentivity of nonvolatile memory used for the storage
of multiple potentiometer settings or data.
In addition, the packages of the potentiometers are
completely compatible with other electronic components and
hence reduce manufacturing assembly costs.
Intersil’s potentiometers are controlled through the 2-wire, I2C,
3-wire, or SPI computer serial-interfaces or buses. For front
panel, push button type applications, Intersil’s push pots are
recommended.
Applications
VR
VR
VW
I
THREE TERMINAL POTENTIOMETER;
VARIABLE VOLTAGE DIVIDER
TWO TERMINAL VARIABLE RESISTOR;
VARIABLE CURRENT
FIGURE 1. BASIC CONFIGURATIONS OF ELECTRONIC POTENTIOMETERS
January 9, 2013
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
Copyright Intersil Americas Inc. 2013. All Rights Reserved.
1-888-INTERSIL or 1-888-468-3774 | 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 1145
Application Circuits
+V
+V
R1
+V
+5V
VW
VREF
ISL28177
+
VOUT
–
X
VW
+V
–5V
VW
VOUT = VW
(a)
FIGURE 3. CASCADING TECHNIQUES
FIGURE 2. BUFFERED REFERENCE VOLTAGE
VS
(b)
ISL28110
+
VIN
VO
–
VO (REG)
317
R1
R2
Iadj
R1
R2
VO = (1+R2/R1)VS
VO (REG) = 1.25V (1+R2/R1)+Iadj R2
FIGURE 4. NONINVERTING AMPLIFIER
FIGURE 5. VOLTAGE REGULATOR
+5V
R1
R2
VS
VS
2.2kΩ
ISL28915
–
100kΩ
+
–
VO
VO
+
ISL28110
+12V
10kΩ
-12V
FIGURE 6. OFFSET VOLTAGE ADJUSTMENT
2
}
10kΩ
}
10kΩ
R1
R2
VUL = {R1/(R1+R2)} VO(MAX)
VLL = {R1/(R1+R2)} VO(MIN)
FIGURE 7. COMPARATOR WITH HYSTERISIS
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Application Note 1145
Application Circuits (Continued)
C
VS
+
VO
R2
R1
–
–
VS
R
VO
+
ISL28108
R3
R4
R2
R1 = R 3 = R4
R1
R2 = 2R1
GO = 1 + R2/R1
fc = 1/(2πRC)
V O = G VS
-1/2 ≤ G ≤ +1/2
FIGURE 8. ATTENUATOR
FIGURE 9. FILTER
R2
C1
R2
VS
}
}
R1
ISL28117
VS
ISL28117
+
–
–
VO
+
R1
ZIN
ISL28107
R3
ZIN = R2 + s R2 (R1 + R3) C1 = R2 + s Leq
(R1 + R3) >> R2
VO = G VS
G = - R2/R1
FIGURE 10. INVERTING AMPLIFIER
FIGURE 11. EQUIVALENT L-R CIRCUIT
C
R2
–
R1
–
+
ISL28217
} RA
+
ISL28217
} RB
FREQUENCY ∝ R1, R2, C
AMPLITUDE ∝ RA, RB
FIGURE 12. FUNCTION GENERATOR
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Application Note 1145
Application Circuits (Continued)
R1
R1
R3
VR
R2
R1
+
R1
–
VO
+
IS
IS
R
–
ISL28110
RL
ISL28210
R1
+
–
VO / IS = -R3(1+R2/R1) + R2
IS = VR/R
FIGURE 13. I TO V CONVERTER
FIGURE 14. CURRENT SOURCE
R1
VS
ISL28217
R1
–
+
C
–
+
–
VO
R2
R1
+
ISL28217
C
ISL28110
R
Cin
CIN = C (1 + R2/R1)
VO/VS = 180° – 2tan-1ω RC
FIGURE 15. PHASE SHIFTER
FIGURE 16. CAPACITANCEV MULTIPLIER
2R
VS
R
R
R
R1
–
–
+
+
VO
A2
ISL28217
A1
ISL28217
VO = |VS|
R1
R
FIGURE 17. ABSOLUTE VALUE AMPLIFIER WITH GAIN
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Application Note 1145
Application Circuits (Continued)
VREFERENCE (VR)
+
VS
ISL28108
}
R2
}
R1
–
VH
ISL28108
VW
VOUT
–
+
VOUT
+
+
VR
VL
+
VTRANSDUCER (VT)
VOUT = HIGH FOR VS ≤
VOUT = LOW FOR VS ≥
R1
R2
R1
R2
–
VR
VR
VT > VW, VOUT = HIGH
R1 + R2 = RPOT
VT < VW, VOUT = LOW
FIGURE 18. LEVEL DETECTOR
FIGURE 19. LEVEL DETECTOR
VH
R
+5V
–
ISL28113
V+
VOUT
+
V–
VL VW
R2
C
R3
+5V
R1
Frequency ∝ R, C
Duty Cycle ∝ R1, R2, R3
FIGURE 20. OSCILLATOR
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Application Note 1145
Application Circuits (Continued)
VOUT
+5V
VH
+5V
VS
VW
+5V
t
ISL28113
–
VW
VNI
VOUT
+5V
+
t
+5V
VOUT
VL
t
Δt
VNI
VS
R
C
Δt = RCln
5V
( 5V – VW )
FIGURE 21. TIME DELAY
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
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