X90100 Datasheet, PDF (8/10 Pages) Xicor Inc. – NV Electronically Programmable Capacitor

X90100
When the device 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 capacitor is set to the
value last stored.
INSTRUCTIONS AND PROGRAMMING
The INC, U/D and CS inputs control the movement of
the capacitor total value. With CS set LOW the device
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 capacitor combinations for
the capacitor array.
The value of the counter is stored in nonvolatile mem-
ory whenever CS transitions HIGH while the INC input
is also HIGH.
The system may select the X90100, move the capaci-
tor value and deselect the device without having to
store the latest count total in nonvolatile memory. After
the count movement is performed as described above
and once the new position is reached, the system must
keep INC LOW while taking CS HIGH. The new C_TO-
TAL ^{value will be maintained until changed by the sys-}
tem or until a power-up/down cycle recalled the
previously stored data.
This procedure allows the system to always power-up
to a preset value stored in nonvolatile memory; then
during system operation minor adjustments can be
made. The adjustments might be based on user prefer-
ence, 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 device
and then move the counter up and down until the
proper trim is attained.
MODE SELECTION
CS INC U/D
Mode
L
H Cap value Up
L
L Cap value Down
H
X Store Cap Position
H
X
X Standby Current
L
X No Store, Return to Standby
L
H Cap value Up
(not recommended)
L
L Cap value Down
(not recommended)
TABLE OF VALUES
Single-Ended Mode
C_OUT = ^Code • 7.0 + 7.5 (pF)
31
0 ≤ Code ≤ 31
Differential Mode
C_OUT = Code • 0.35 + 1.00 (pF)
0 ≤ Code ≤ 31
C_p
X90100
C_m
X1
Oscillator
Circuit
X2
C_m
C_p
X90100
C_p
Oscillator
Circuit
C_s
Example of a single-ended circuit
REV 1.4.7 9/8/03
Example of a differential mode circuit
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