X9C102, X9C103, X9C104, X9C503

FN8222 Rev 4.00

Page 6 of 12

Jan 11, 2019

AC Timing Diagram

Pin Descriptions

RH/VH and RL/VL

The high (VH/RH) and low (VL/RL) terminals of the ISLX9C102,

X9C103, X9C104, X9C503 are equivalent to the fixed

terminals of a mechanical potentiometer. The minimum voltage

is -5V and the maximum is +5V. The terminology of VH/RH and

V

L

/R

L

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

VW/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 40

.

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 non-volatile memory when CS is

returned HIGH while the INC input is also HIGH. After the store

operation is complete the ISLX9C102, X9C103, X9C104,

X9C503 device will be placed in the low power standby mode

until the device is selected once again.

Principles of Operation

There are three sections of the X9C102, X9C103, ISL9C104

and ISL9C503: the input control, counter and decode section;

the non-volatile 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 non-volatile memory and retained for future use. The

resistor array is comprised of 99 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.

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/RW 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 last wiper position

stored will be maintained in the non-volatile memory. When

power is restored, the contents of the memory are recalled and

the wiper is reset to the value last stored.

The internal charge pump allows a wide range of voltages

(from -5V to 5V) applied to XDCP terminals yet given a

convenience of single power supply. The typical charge pump

noise of 20mV at 850kHz should be taken in consideration

when designing an application circuit.

CS

INC

U/D

VW

tCI

tIL

tIH

tCYC

tID

tDI

tIW

MI

tIC

tCPH

tF

tR

10%

90%

90%

(NOTE)

NOTE: MI REFERS TO THE MINIMUM INCREMENTAL CHANGE IN THE VW OUTPUT DUE TO A CHANGE IN THE WIPER POSITION.