X9316 Datasheet, PDF (3/12 Pages) Xicor Inc. – E 2 POT™ Nonvolatile Digital Potentiometer

X9316
DEVICE OPERATION
There are three sections of the X9316: 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 trans-
fers the potential at that point to the wiper.
The INC, U/D and CS inputs control the movement of the
wiper along the resistor array. With CS set LOW the
X9316 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 seven bit counter. The output of this counter
is decoded to select one of thirty two wiper positions
along the resistive array.
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.
The value of the counter is stored in nonvolatile memory
whenever CS transistions HIGH while the INC input is
also HIGH.
When the X9316 is powered-down, the last counter posi-
tion stored will be maintained in the nonvolatile memory.
When power is restored, the contents of the memory are
recalled and the counter is reset to the value last stored.
Operation Notes
The system may select the X9316, move the wiper and
deselect the device without having to store the latest
wiper position in nonvolatile memory. The wiper move-
ment is performed as described above; once the new
position is reached, the system would the keep INC LOW
while taking CS HIGH. The new wiper position would be
maintained until changed by the system or until a power-
up/down cycle recalled the previously stored data.
This would allow the system to always power-up to a pre-
set value stored in nonvolatile memory; then during sys-
tem operation minor adjustments could be made. The
adjustments might be based on user preference, system
parameter changes due to temperature drift, etc...
The state of U/D may be changed while CS remains
LOW. This allows the host system to enable the X9316
and then move the wiper up and down until the proper
trim is attained.
T_IW/R_TOTAL
The electronic switches on the X9316 operate in a “make
before break” mode when the wiper changes tap posi-
tions. If the wiper is moved several positions multiple taps
are connected to the wiper for t_IW (INC to V_W change).
The R_TOTAL value for the device can temporarily be
reduced by a significant amount if the wiper is moved
several positions.
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
3