X1228 Datasheet, PDF (17/31 Pages) Xicor Inc. – Real Time Clock/Calendar/CPU Supervisor with EEPROM

X1228
Figure 5. Set V_TRIP Level Sequence (V_CC = desired V_TRIP value)
RESET
V_CC
SCL
0 1 23 4 56 7
V_P = 15V
01 23 4 56 7
01 23 4 56 7
V_CC
01 23 4 56 7
SDA
AEh
00h
Note: BP0, BP1, BP2 must be disabled.
01h
00h
Resetting the V_TRIP Voltage
This procedure is used to set the V_TRIP to a “native”
voltage level. For example, if the current V_TRIP is 4.4V
and the new V_TRIP must be 4.0V, then the V_TRIP must
be reset. When V_TRIP is reset, the new V_TRIP is some-
thing less than 1.7V. This procedure must be used to
set the voltage to a lower value.
To reset the new V_TRIP voltage, apply more than 5.5V
to the V_CC pin and tie the RESET pin to the
programming voltage V_P. Then write 00h to address
03h. The stop bit of a valid write operation initiates the
V_TRIP programming sequence. Bring RESET to V_CC to
complete the operation. Note: this operation takes up
Figure 6. Reset V_TRIP Level Sequence
to 10 milliseconds to complete and also writes 00h to
address 03h of the EEPROM array.
For best accuracy in setting V_TRIP, it is advised that the
following sequence be used.
1.Program V_TRIP as above.
2.Measure resulting V_TRIP by measuring the V_CC
value where a RESET occurs. Calculate Delta =
(Desired – Measured) V_TRIP value.
3.Perform a V_TRIP program using the following formula
to set the voltage of the RESET pin:
V_RESET = (Desired Value – Delta) + 0.025V
RESET
V_CC
SCL
V_P = 15V
V_CC
01234567 01234567 01234567 01234567
SDA
AEh
00h
03h
00h
Note: BP0, BP1, BP2 must be disabled.
REV 1.3 3/24/04
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Characteristics subject to change without notice. 17 of 31