7
FN8083.1
August 27, 2015
On applying power to the ISL95310, the V
CC
supply should
have a monotonic ramp to the specified operating voltage. It
is important that once V
CC
reaches 1V that it increases to at
least 2.5V in less than 7.5ms (0.2V/ms). The ramp rate
before and after these thresholds is not important.
V
CC
must be applied prior to, or simultaneously, with V+.
Under no condition should V+ be applied without V
CC
. While
the sequence of applying V+ and V
CC
to the ISL95310 does
not affect the proper recall of the wiper position, applying V+
before V
CC
powers the electronic switches of the DCP
before the electronic switch control signals are applied. This
can result in multiple electronic switches being turned on,
which could load the power supply and cause brief,
unexpected potentiometer wiper settings.
To prevent unknown wiper positions on the ISL95310 on
power down, it is recommended that V+ turn off before or
simultaneously with V
CC
. If V+ remains on after V
CC
turns
off, the wiper position can remain unchanged from its
previous setting or it can go to an undefined state.
Instructions and Programming
The INC, U/D and CS inputs control the movement of the
wiper along the resistor array. 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 seven
bit counter. The output of this counter is decoded to select
one of one hundred wiper positions along the resistive array.
The value of the counter is stored in nonvolatile memory
whenever CS
transitions HIGH while the INC input is also
HIGH.
The system may select the ISL95310, move the wiper and
deselect the device without having to store the latest wiper
position in nonvolatile memory. After the wiper 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 wiper position will be maintained until
changed by the system 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 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 device and then
move the wiper up and down until the proper trim is attained.
During initial power-up CS
must go high along with or before
V
CC
to avoid an accidental store generation.
TABLE 1. MODE SELECTION
CS
INC U/D MODE
L H Wiper up
L L Wiper down
H X Store wiper position
H X X Standby current
L X No store, return to standby
H H X Standby
L H Wiper up one position
(not recommended)
L L Wiper down one position
(not recommended)
ISL95310
