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FN8178.3

July 24, 2014

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Typical Attenuation Characteristics (dB)

Principles of Operation

There are three sections of the X9314: the input control,

counter and decode section; the nonvolatile 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 nonvolatile memory

and retained for future use. The resistor array is comprised of

31 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 INC, U/D and CS inputs control the movement of the

wiper along the resistor array. With CS set LOW the X9314

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 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 value of the counter is stored in nonvolatile memory

whenever CS transistions HIGH while the INC input is also

HIGH.

When the X9314 is powered down, the last counter position

stored will be maintained in the nonvolatile memory. When

power is restored, the contents of the memory are recalled

and the counter is reset to the value last stored.

Operation Notes

The system may select the X9314, move the wiper and

deselect the device without having to store the latest wiper

position in nonvolatile memory. The wiper movement is

performed as described above; once the new position is

reached, the system would keep the INC LOW while taking

CS HIGH. The new wiper position would be maintained until

changed by the system or until a power-up/down cycle

recalled the previously stored data.

This would allow the system to always power up to a preset

value stored in nonvolatile memory; then during system

operation minor adjustments could be made. The

adjustments might be based on user preference, system

parameter changes due to temperature drift, etc.

The state of U/D may be changed while CS remains LOW.

This allows the host system to enable the X9314 and then

move the wiper up and down until the proper trim is attained.

The electronic switches on the X9314 operate in a “make

before break” mode when the wiper changes tap positions. If

the wiper is moved several positions multiple taps are

a significant amount if the wiper is moved several positions.

Power-up and Down Requirement

voltages applied to the potentiometer pins during power-up

or power-down conditions. During power-up, the data sheet

parameters for the DCP do not fully apply until 1 millisecond

always in effect.

TAP POSITION

0

4

8

12

16

20

24

28

31

-20

-40

-43.5

0

-60

X9314