X93256 Datasheet, PDF (8/9 Pages) Intersil Corporation – Dual Digitally Controlled Potentiometers

X93256
INSTRUCTIONS AND PROGRAMMING
The INC, U/D and CS inputs control the movement of the
pertaining wiper along the resistor array. With CS set
LOW the pertaining potentiometer is selected and
enabled to respond to the U/D and INC inputs. HIGH to
LOW transitions on INC will increment or decrement
(depending on the state of the U/D input) a five bit
counter. The output of this counter is decoded to select
one of thirty two wiper positions along the resistive array.
The value of the counter is stored in nonvolatile memory
whenever each CS transitions HIGH while the pertaining
INC input is also HIGH. In order to avoid an accidental
store during power-up, each CS must go HIGH with V_CC
during initial power-up. When left open, each CS pin is
internally pulled up to V_CC by an internal 30K resistor.
The system may select the X93256, move any wiper and
deselect the device without having to store the latest
wiper position in nonvolatile memory. After the wiper
movement is 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.
In order to recall the stored position of the wiper on
power-up, the CS pin must be held HIGH.
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, or other
system trim requirements.
The state of U/D may be changed while CS remains
LOW. This allows the host system to enable the device
and then move each wiper up and down until the proper
trim is attained.
MODE SELECTION
CS INC U/D
Mode
L
H Wiper Up
L
L Wiper Down
H
X Store Wiper Position
H
X
X Standby Current
L
X No Store, Return to Standby
L
H Wiper Up (not recommended)
L
L Wiper Down (not recommended)
SYMBOL TABLE
WAVEFORM INPUTS
OUTPUTS
Must be
steady
May change
from Low to
High
May change
from High to
Low
Don’t Care:
Changes
Allowed
N/A
Will be
steady
Will change
from Low to
High
Will change
from High to
Low
Changing:
State Not
Known
Center Line
is High
Impedance
8
FN8188.0
March 4, 2005