X90100 Datasheet, PDF (7/10 Pages) Xicor Inc. – NV Electronically Programmable Capacitor

X90100
PIN CONFIGURATION
INC
U/D
Vss
Cp
MSOP
1
8
2
7
X90100
3
6
4
5
V_CC
CS
N/C (leave floating)
Cm
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
trimmable capacitor. The minimum dc voltage is V_SS
and the maximum is V_CC. The value of capacitance
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
Symbol
Cp
Cm
V_SS
V_CC
U/D
INC
CS
Default
output
output
supply
supply
pull up
pull up
pull up
Description
Positive capacitor terminal
Negative capacitor terminal
Ground
Positive supply voltage
Up/Down control input
Increment control input
Chip Select control input
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,
multiple units are connected to the total for t_IW (INC to
C_TOTAL change). The C_TOTAL value for the device can
temporarily be increased by a significant amount if the
counter is moved several positions.
REV 1.4.7 9/8/03
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