X93256 Datasheet, PDF (7/9 Pages) Intersil Corporation – Dual Digitally Controlled Potentiometers

X93256
PIN DESCRIPTIONS
(In the text, CS, INC, U/D, R_H, R_W, and R_L are used to
refer to either CS₁ or CS₂, etc. Note: These signals can
be applied independently or at the same time.)
R_H and R_L
The R_H and R_L pins of the X93256 are equivalent to the
fixed terminals of a mechanical potentiometer. The
minimum voltage is V_SS and the maximum is V_CC. The
terminology of R_H and R_L references the relative position
of the terminal in relation to wiper movement direction
selected by the U/D input per potentiometer.
R_W
The R_W pin of the X93256 is the wiper terminal of the
potentiometer which is equivalent to the movable terminal of
a mechanical potentiometer
Up/Down (U/D)
The U/D input controls the direction of a single
potentiometer’s wiper movement and whether the
counter is incremented or decremented.
Increment (INC)
The INC input is negative-edge triggered. Toggling INC
will move the wiper and either increment or decrement
the pertatining potentiometer’s counter in the direction
indicated by the logic level on the pertaining
potentiometer’s U/D input.
Chip Select (CS)
A potentiometer is selected when the pertaining CS input
is LOW. Its current counter value is stored in nonvolatile
memory when the pertaining CS is returned HIGH while
the pertaining INC input is also HIGH. After the store
operation is complete the affected potentiometer will be
placed in the low power standby mode until the
potentiometer is selected once again.
PRINCIPLES OF OPERATION
There are multiple sections for each potentiometer in the
X93256: an input control, a counter and decode section;
the nonvolatile memory; and a resistor array. Each 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. Under the proper conditions the
contents of the counter can be stored in nonvolatile
memory and retained for future use. Each 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.
Each 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_IW (INC to V_W change). The
2-terminal resistance value for the device can temporarily
change by a significant amount if the wiper is moved
several positions.
When the device is powered-down, the last wiper
position stored will be maintained in the nonvolatile
memory for each potentiometer. When power is
restored, the contents of the memory are recalled and
each wiper is set to the value last stored.
7
FN8188.0
March 4, 2005