X93154 Datasheet, PDF (5/9 Pages) Intersil Corporation – Digitally Controlled Potentiometer

X93154
Pin Descriptions
R_H and R_L
The R_H and R_L pins of the X93154 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.
Up/Down (U/D)
The U/D input controls the direction of the 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
counter in the direction indicated by the logic level on the
U/D input.
Chip Select (CS)
The device is selected when the CS input is LOW. The
current counter value is stored in nonvolatile memory when
CS is returned HIGH while the INC input is also HIGH. After
the store operation is complete the X93154 will be placed in
the low power standby mode until the device is selected
once again.
Pin Configuration
INC
U/D
R_H/V_H
V_SS
MSOP
1
8
2
7
X93154
3
6
4
5
V_CC
CS
R_L/V_L
NC*
*NC = No Connect. Can be connected to any
voltage between V_SS and V_CC, or left unconnected.
Pin Names
SYMBOL
RH
RL
VSS
VCC
U/D
INC
CS
DESCRIPTION
High terminal
Low terminal
Ground
Supply voltage
Up/Down control input
Increment control input
Chip Select control input
Principles of Operation
There are three sections of the X93154: the input control,
counter and decode section; the nonvolatile memory; 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. Under the proper
conditions the contents of the counter can be stored in
nonvolatile memory and retained for future use. 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, 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. When
power is restored, the contents of the memory are recalled
and the wiper is set to the value last stored.
Instructions and Programming
The INC, U/D and CS inputs control the movement of the
wiper along the resistor array. With CS set LOW the device
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 CS transitions HIGH while the INC input is also
HIGH. In order to avoid an accidental store during power-up,
CS must go HIGH with V_CC during initial power-up. When
performing multiple write operations, V_CC must not decrease
by more than 150mV from its initial value. When left open,
the CS pin is internally pulled up to V_CC by an internal 30k
resistor.
The system may select the X93154, move the 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.
5
FN8180.2
October 5, 2005