X4043/45
Setting a V
TRIP
Voltage
There are two procedures used to set the threshold
voltages (V
TRIP
), depending if the threshold voltage to
be stored is higher or lower than the present value. For
example, if the present V
TRIP
is 2.9 V and the new
V
TRIP
is 3.2 V, the new voltage can be stored directly
into the V
TRIP
cell. If however, the new setting is to be
lower than the present setting, then it is necessary to
“reset” the V
TRIP
voltage before setting the new value.
Setting a Higher V
TRIP
Voltage
To set a V
TRIP
threshold to a new voltage which is
higher than the present threshold, the user must apply
the desired V
TRIP
threshold voltage to the V
CC
. Then, a
programming voltage (Vp) must be applied to the WP
pin before a START condition is set up on SDA. Next,
issue on the SDA pin the Slave Address A0h, followed
by the Byte Address 01h for V
TRIP
and a 00h Data
Byte in order to program V
TRIP
. The STOP bit following
a valid write operation initiates the programming
sequence. WP pin must then be brought LOW to com-
plete the operation.
To check if the V
TRIP
has been set, first power down
the device. Slowly ramp up V
CC
and observe when the
output, RESET (4043) or RESET (4045) switches. The
voltage at which this occurs is the V
TRIP
(actual) (see
Figure 2).
C
ASE
A
Now if the desired V
TRIP
is greater than the V
TRIP
(actual), then add the difference between V
TRIP
(desired) – V
TRIP
(actual) to the original V
TRIP
desired.
This is your new V
TRIP
that should be applied to V
CC
and the whole sequence should be repeated again
(see Figure 5).
C
ASE
B
Now if the V
TRIP
(actual), is higher than the V
TRIP
(desired), perform the reset sequence as described in
the next section. The new V
TRIP
voltage to be applied
to V
CC
will now be: V
TRIP
(desired) – (V
TRIP
(actual) –
V
TRIP
(desired)).
Note:
This operation does not corrupt the memory
array.
Setting a Lower V
TRIP
Voltage
In order to set V
TRIP
to a lower voltage than the
present value, then V
TRIP
must first be “reset” accord-
ing to the procedure described below. Once V
TRIP
has
been “reset”, then V
TRIP
can be set to the desired volt-
age using the procedure described in “Setting a Higher
V
TRIP
Voltage”.
Resetting the V
TRIP
Voltage
To reset a V
TRIP
voltage, apply the programming volt-
age (Vp) to the WP pin before a START condition is set
up on SDA. Next, issue on the SDA pin the Slave
Address A0h followed by the Byte Address 03h fol-
lowed by 00h for the Data Byte in order to reset V
TRIP
.
The STOP bit following a valid write operation initiates
the programming sequence. Pin WP must then be
brought LOW to complete the operation.
After being reset, the value of V
TRIP
becomes a nomi-
nal value of 1.7V or lesser.
Note:
This operation does not corrupt the memory
array.
REV 1.1.17 9/14/01
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Characteristics subject to change without notice.
4 of 25
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