6

FN8222.3

July 20, 2009

AC Timing Diagram

Pin Descriptions

L

/R

L

) 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

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.

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

Ω.

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

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

MI

10%

90%

90%

(NOTE)

X9C102, X9C103, X9C104, X9C503