X9319_14 Datasheet, PDF (6/8 Pages) Intersil Corporation – Digitally Controlled Potentiometer

X9319
performed as described above and once the new position is
reached, the system must keep INC LOW while taking CS
HIGH. The new wiper position will be maintained until changed
by the system or until a power-up/down cycle recalled the
previously stored data. This procedure allows the system to
always power-up to a preset value stored in nonvolatile
memory; then during system operation minor adjustments
could be made. The adjustments might be based on user
preference, system parameter changes due to temperature
drift, etc.
The state of U/D may be changed while CS remains LOW. This
allows the host system to enable the device and then move the
wiper up and down until the proper trim is attained.
Mode Selection
CS
INC
U/D
L
H
Wiper up
MODE
L
L Wiper down
Mode Selection (Continued)
CS
INC
U/D
MODE
H
X Store wiper position to
nonvolatile memory
H
X
X Standby
L
X No store, return to standby
L
H Wiper Up (not recommended)
L
L Wiper Down
(not recommended)
Applications Information
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.
Basic Configurations of Electronic Potentiometers
V_REF
R_H
V_REF
R_W
R_L
FIGURE 1. THREE TERMINAL POTENTIOMETER; VARIABLE
VOLTAGE DIVIDER
I
FIGURE 2. TWO TERMINAL VARIABLE RESISTOR; VARIABLE
CURRENT
Basic Circuits
+V
+V
R₁
+V
V_REF
+5V
R_W
+
LMC7101
-
V_OUT
V_OUT = V_W/R_W
FIGURE 3. BUFFERED REFERENCE VOLTAGE
X
R_W
+V
R_W
(a)
(b)
FIGURE 4. CASCADING TECHNIQUES
R₁ R₂
+8V
V_S
100k
+10V
-
+
100k
V_O
LMC7101
V_O = (R₂/R₁)V_S
FIGURE 5. SINGLE SUPPLY
INVERTING AMPLIFIER
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FN8185.3
July 31, 2014