X4043 Datasheet, PDF (6/24 Pages) Intersil Corporation – CPU Supervisor with 4kbit EEPROM

X4043, X4045
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 program-
ming sequence. WP pin must then be brought LOW to
complete 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).
CASE 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).
CASE 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.
6
FN8118.1
September 30, 2005