X9317 Datasheet, PDF (9/15 Pages) Intersil Corporation – Low Noise, Low Power, 100 Taps

X9317
Pin Descriptions
R_H and R_L
The high (R_H) and low (R_L) terminals of the X9317 are
equivalent to the fixed terminals of a mechanical
potentiometer. The terminology of R_L and R_H 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.
R_W
R_w 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.
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 X9317 will be placed in
the low power standby mode until the device is selected
once again.
Pin Configuration
DIP/SOIC/MSOP
INC
U/D
R_H
V_SS
1
8
2 _X9317 7
3
6
4
5
V_CC
CS
R_L
R_W
CS
V_CC
INC
U/D
TSSOP
1
8
2 _X9317 7
3
6
4
5
R_L/V_L
R_W/V_W
V_SS
R_H/V_H
Pin Names
SYMBOL
RH
RW
RL
VSS
VCC
U/D
INC
CS
DESCRIPTION
High terminal
Wiper terminal
Low terminal
Ground
Supply voltage
Up/Down control input
Increment control input
Chip select control input
Principles of Operation
There are three sections of the X9317: the control section,
the nonvolatile memory, and the resistor array. The 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 contents of the counter can be stored in nonvolatile
memory and retained for future use. The resistor array is
comprised of 99 individual resistors connected in series.
Electronic switches at either end of the array and between
each resistor provide an electrical connection to the wiper
pin, R_W.
The wiper acts like its mechanical equivalent and does not
move beyond the first or 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 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.
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 seven
bit counter. The output of this counter is decoded to select
one of one hundred 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.
9
FN8183.1
September 9, 2005