VH /RH and VL /RL
The high (VH/RH) and low (VL/RL) terminals of the
X9116 are equivalent to the ﬁxed terminals of a
mechanical potentiometer. The minimum voltage is
VSS and the maximum is VCC.
Rw/Rw is the wiper terminal and is equivalent to the
movable terminal of a mechanical potentiometer. The
position of the wiper within the array is determined by
the control inputs. The wiper terminal series resistance
is typically 200Ω to 400Ω depending upon VCC.
The U/D input controls the direction of the wiper move-
ment and whether the counter is incremented (up) or
The INC input is negative-edge triggered. Toggling
INC will move the wiper and either increment or decre-
ment 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 X9116
will be placed in the low power standby mode until the
device is selected once again.
Up/Down Control Input
Increment Control Input
Chip Select Input
PRINCIPLES OF OPERATION
There are three sections of the X9116: the input con-
trol, counter and decode section; the nonvolatile mem-
ory; 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 com-
prised of 15 individual resistors connected in series. At
either end of the array and between each resistor is an
electronic switch that transfers the potential at that
point to the wiper pin.
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 electronic switches on the device operate in a
“make before break” mode when the wiper changes
tap positions. If the wiper is moved several positions,
multiple taps are connected to the wiper for tIW (INC to
VW change). The RTOTAL value for the device can tem-
porarily be reduced by a signiﬁcant amount if the wiper
is moved several positions.
When the device is powered-down, the last wiper posi-
tion stored will be maintained in the nonvolatile mem-
ory. When power is restored, the contents of the
memory are recalled and the wiper is set to the value
REV 1.2 2/5/03
Characteristics subject to change without notice. 2 of 11