X9514 Datasheet, PDF (3/11 Pages) Xicor Inc. – PushPot™ Potentiometer (Push Button Controlled)

X9514
DEVICE OPERATION
There are three sections of the X9514: the input control,
counter and decode section; the E²PROM 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 E²PROM 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 trans-
fers the potential at that point to the wiper.
The X9514 is designed to interface directly to two push
button switches for effectively moving the wiper up or
down. The PU and PD inputs increment or decrement a
5-bit counter respectively. The output of this counter is
decoded to select one of the thirty-two wiper positions
along the resistive array. The wiper increment input, PU
and the wiper decrement input, PD are both connected
to an internal pull-up so that they normally remain HIGH.
When pulled LOW by an external push button switch or
a logic LOW level input, the wiper will be switched to the
next adjacent tap position.
Internal debounce circuitry prevents inadvertent switch-
ing of the wiper position if PU or PD remain LOW for less
than 40ms, typical. Each of the buttons can be pushed
either once for a single increment/decrement or continu-
ously for a multiple increments/decrements. The num-
ber of increments/decrements of the wiper position
depend on how long the button is being pushed. When
Typical circuit with ASE store pin controlled by
push button switch
V_CC
8 _VCC
1 _PU
2 _PD
7 _ASE
VH ³
VW ⁵
VL 6
V_SS
making a continuous push, after the first second, the
increment/decrement speed increases. For the first
second the device will be in the slow scan mode. Then
if the button is held for longer than 1 second the device
will be in the fast scan mode. As soon as the button is
released the X9514 will return to a standby condition.
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.
AUTOSTORE
The value of the counter is stored in E²PROM memory
whenever the chip senses a powers-down of V_CC while
ASE is enabled (held LOW). When power is restored,
the content of the memory is recalled and the counter
reset to the last value stored.
If AUTOSTORE is to be implemented, ASE is typically
hard wired to V_SS. If ASE is held HIGH during power up
and then taken LOW, the wiper will not respond to the
PU or PD inputs until ASE is brought HIGH and held
HIGH.
Manual (Push Button) Store
When ASE is not enabled (held HIGH) a push button
switch may be used to pull ASE LOW and released to
perform a manual store of the wiper position.
R_TOTAL with V_CC Removed
The end to end resistance of the array will fluctuate once
V_CC is removed.
Typical circuit with ASE store pin used in
AUTOSTORE mode
V_CC
3.3µF
8 _VCC
1 _PU
2 _PD
7 _ASE
V_SS ⁴
VH ³
VW ⁵
VL ⁶
6487 ILL F05a
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6487 ILL F05.2