RH/VH and RL/VL
The high (RH/VH) and low (RL/VL) terminals of the X9015 are
equivalent to the fixed terminals of a mechanical potentiometer.
The minimum voltage is VSS and the maximum is VCC. The
terminology of RL/VL and RH/VH references the relative position
of the terminal in relation to wiper movement direction selected
by the U/D input, and not the voltage potential on the terminal.
RW/Vw 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 200 at VCC=5V.
At power up the wiper position is at Tap #15. (VL/RL=Tap #0).
The U/D input controls the direction of the wiper movement and
whether the tap position is incremented or decremented.
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. When CS is
returned HIGH while the INC input is also HIGH the X9015 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 control input
Principles Of Operation
There are two sections of the X9015: the input control, counter
and decode section; 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. The
resistor array is comprised of 31 individual resistors connected
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
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 temporarily be reduced by a significant amount if the
wiper is moved several positions.
When the device is powered-down, the wiper position is lost.
When power is restored, the wiper is set to Tap #15.
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 system may select the X9015, move the wiper and deselect
the device. The new wiper position will be maintained until
changed by the system or until a power-up/down cycle.
The state of U/D may be changed while CS remains LOW. This
allows the host system to enable the device and then move the
wiper up and down until the proper trim is attained.
CS INC U/D
Wiper Up (not recommended)
Wiper Down (not recommend-
FN8157 Rev 6.00
August 14, 2015
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