ISL90460 Intersil Corporation, ISL90460 Datasheet - Page 5

• Manufacturer Part Number: ISL90460
• Description: Digitally Controlled Potentiometer
• Manufacturer: Intersil Corporation

Pin Descriptions
RH
The ISL90460 contains a digital potentiometer connected as
a rheostat or variable resistor. The wiper and one terminal of
the digital potentiometer is tied to the RH pin, and the other
terminal of the potentiometer is tied to the ground pin (GND).
The resistance from the RH pin to ground will vary with the
potentiometer setting; at the highest setting, the resistance
will be the maximum (Rtot), at the lowest setting it will be a
minimum.
Up/Down (U/D)
The U/D input controls the direction of the wiper movement
and whether the counter is incremented or decremented.
Chip Select (CS)
The device is selected when the CS input is LOW. The
current counter value is stored in volatile memory when CS
is returned HIGH. When CS is high, the device is placed in
low power standby mode.
U/D
RH
CS
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FIGURE 2. SERIAL INTERFACE TIMING DIAGRAM, DECREMENT
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CU
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CI
ISL90460
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IH
Principles of Operation
There are two sections of the ISL90460: the input control,
counter and decode section; and the resistor array. The input
control section operates just like an up/down counter. The
output of this counter is decoded to turn on a single
electronic switch connecting a point on the resistor array to
the wiper output. The resistor array is comprised of 31
individual resistors connected in series. At either end of the
array and between each resistor is an electronic switch that
transfers the connection at that point to the wiper. The wiper
is connected to the RH terminal, forming a variable resistor
from RH to GND.
The direction of the wiper movement is defined when the
device is selected. If during CS transition from High to Low
the U/D input is LOW, the wiper will move down on each
rising edge of U/D toggling. Similarly, the wiper will move up
on each rising edge of U/D toggling if, during CS transition
from High to Low, the U/D input is High.
The wiper, when at either fixed terminal, acts like its
mechanical equivalent and does not move beyond the last
position. That is, the counter does not wrap around when
clocked to either extreme.
If the wiper is moved several positions, multiple taps are
connected to the wiper for t
2-terminal resistance value for the device can temporarily
change by a significant amount if the wiper is moved several
positions.
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IL
t
SETTLE
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SETTLE
(U/D to RH change). The
October 7, 2005
June 6, 2005
FN8225.3
FN8225.2