X1227 Xicor, X1227 Datasheet - Page 9

• Manufacturer Part Number: X1227
• Description: Real Time Clock/Calendar/CPU Supervisor with EEPROM
• Manufacturer: Xicor

V
[OPTIONAL]
The X1227 is shipped with a standard V
(V
operating and storage conditions. However, in applica-
tions where the standard V
higher precision is needed in the V
X1227 threshold may be adjusted. The procedure is
described below, and uses the application of a nonvol-
atile write control signal.
X1227
Figure 4. Power On Reset and Low Voltage Reset
Figure 5. Set V
Resetting the V
This procedure is used to set the V
voltage level. For example, if the current V
and the new V
be reset. When V
thing less than 1.7V. This procedure must be used to
set the voltage to a lower value.
To reset the new V
to the V
programming voltage V
03h. The stop bit of a valid write operation initiates the
V
complete the operation. Note: this operation takes up
REV 1.1.20 1/13/03
RESET
CC
Note: BP0, BP1, BP2 must be disabled.
TRIP
TRIP
V
SDA
SCL
CC
THRESHOLD RESET PROCEDURE
) voltage. This value will not change over normal
programming sequence. Bring RESET to V
CC
RESET
V
pin and tie the RESET pin to the
TRIP
CC
TRIP
0 1 2 3 4 5 6 7
TRIP
TRIP
TRIP
V
must be 4.0V, then the V
Level Sequence (V
TRIP
Voltage
is reset, the new V
t
R
P
voltage, apply more than 5.5V
. Then write 00h to address
AEh
TRIP
t
PURST
is not exactly right, or if
TRIP
TRIP
0 1 2 3 4 5 6 7
CC
TRIP
CC
to a “native”
TRIP
= desired V
value, the
TRIP
threshold
is some-
00h
is 4.4V
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V
CC
must
P
= 15V
to
t
RPD
TRIP
Setting the V
It is necessary to reset the trip point before setting the
new value.
To set the new V
threshold voltage to the V
to the programming voltage V
address 01h. The stop bit following a valid write opera-
tion initiates the V
RESET to V
operation may take up to 10 milliseconds to complete
and also writes 00h to address 01h of the EEPROM
array.
to 10 milliseconds to complete and also writes 00h to
address 03h of the EEPROM array.
For best accuracy in setting V
following sequence be used.
1.Program V
2.Measure resulting V
3.Perform a V
value)
value where a RESET occurs. Calculate Delta =
(Desired – Measured) V
to set the voltage of the RESET pin:
V
RESET
0 1 2 3 4 5 6 7
t
PURST
= (Desired Value – Delta) + 0.025V
01h
CC
TRIP
TRIP
TRIP
to complete the operation. Note: this
TRIP
as above.
Characteristics subject to change without notice.
Voltage
TRIP
program using the following formula
voltage, apply the desired V
TRIP
programming sequence. Bring
CC
TRIP
by measuring the V
0 1 2 3 4 5 6 7
pin and tie the RESET pin
t
P
TRIP
F
. Then write data 00h to
value.
, it is advised that the
00h
V
RVALID
CC
9 of 28
TRIP
V
CC