5
FN8230.4
October 20, 2015
Pin Descriptions
RH and RW
The ISL90462 contains a digital potentiometer with one
terminal tied to the ground pin (GND) of the device. The RH
pin is the other potentiometer terminal, and the RW pin is the
wiper terminal. The position of the wiper is controlled by the
CS
- and U/D- inputs, with a movement "up" connecting the
wiper closer to the RH pin, and movement "down"
connection the wiper closer to the GND pin.
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.
Principles of Operation
There are two sections of the ISL90462: 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 RH
and RW terminals are uncommitted, and can for a variable
voltage divider if RH is connected to a voltage source.
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
SETTLE
(U/D to RW change).
The 2-terminal resistance value for the device can
temporarily change by a significant amount if the wiper is
moved several positions.
CS
U/D
RW
t
CU
t
CI
t
IL
t
IH
t
IC
t
SETTLE
FIGURE 2. SERIAL INTERFACE TIMING DIAGRAM DECREMENT
ISL90462
