7 of 10

REV 1.4.7 9/8/03

www.xicor.com

X90100

PIN CONFIGURATION

DETAILED PIN DESCRIPTIONS

Cp and Cm

The high (Cp) and low (Cm) terminals of the X90100

are equivalent to the fixed terminals of a mechanical

across the terminals is determined by digital inputs

INC, U/D, and CS.

Up/Down (U/D)

The U/D input controls the direction of the trimmed

capacitor value and whether the counter is incre-

mented or decremented. This pin has an active current

source pullup.

Increment (INC)

The INC input is negative-edge triggered. Toggling INC

will move the capacitance value and either increment

or decrement the counter in the direction indicated by

the logic level on the U/D input. This pin has an active

current source pullup.

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

X90100 will be placed in the low power standby mode

until the device is selected once again. This pin has

active circuit source pullup.

N/C - This pin should be left floating.

PIN NAMES

PRINCIPLES OF OPERATION

There are three sections of the X90100: the input con-

trol, counter and decode section; the nonvolatile mem-

ory; and the capacitor array. The input control section

operates just like an up/down counter. The output of

this counter is decoded to turn on electronic switches

connecting internal units to the sum capacitor. Under

the proper conditions the contents of the counter can

be stored in nonvolatile memory and retained for future

use. The capacitor array is comprised of 31 individual

capacitors connected in parallel. At one end of each

element is an electronic switch that connects it to the

sum.

The capacitor, when at either end of the range, 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 counter changes

positions. If the counter is moved several positions,

temporarily be increased by a significant amount if the

counter is moved several positions.

CS

INC

U/D

1

2

3

4

8

7

6

5

X90100

MSOP

N/C (leave floating)

Cm

Vss

Cp

Symbol

Default

Description

Cp

output

Positive capacitor terminal

Cm

output

Negative capacitor terminal

supply

Ground

supply

Positive supply voltage

U/D

pull up

Up/Down control input

INC

pull up

Increment control input

CS

pull up

Chip Select control input