X93155_08 Datasheet, PDF (5/8 Pages) Intersil Corporation – Digitally Controlled Potentiometer(XDCP™)

AC Timing
CS
t_CI
INC
U/D
X93155
t_CYC
t_IL
t_IH
t_IC
t_ID
t_DI
(STORE)
t_CPH
90% 90%
10%
t_F
t_R
Power-up and Power-down Requirements
There are no restrictions on the power-up or power-down
conditions of V_CC and the voltages applied to the
potentiometer pins provided that V_CC is always more
positive than or equal to V_H and V_L, i.e., V_CC ≥ V_H,V_L. The
V_CC ramp rate specification is always in effect.
Pin Descriptions
R_H and R_L
The R_H and R_L pins of the X93155 are equivalent to the end
terminals of a variable resistor. 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 X93155 will be placed in
the low power standby mode until the device is selected
once again.
Principles of Operation
There are three sections of the X93155: 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
5
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 is connected to the R_L terminal,
forming a variable resistor from R_H to R_L.
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 up to 10µs. 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
left open, the CS pin is internally pulled up to V_CC by an
internal 30kΩ resistor.
The system may select the X93155, move the wiper and
deselect the device without having to store the latest wiper
FN8181.2
February 19, 2008