X1227
Figure 4. Power On Reset and Low Voltage Reset
V
TRIP
V
CC
t
PURST
t
RPD
t
R
RESET
t
F
V
RVALID
t
PURST
V
CC
THRESHOLD RESET PROCEDURE
[OPTIONAL]
The X1227 is shipped with a standard V
CC
threshold
(V
TRIP
) voltage. This value will not change over normal
operating and storage conditions. However, in applica-
tions where the standard V
TRIP
is not exactly right, or if
higher precision is needed in the V
TRIP
value, the
X1227 threshold may be adjusted. The procedure is
described below, and uses the application of a nonvol-
atile write control signal.
Setting the V
TRIP
Voltage
It is necessary to reset the trip point before setting the
new value.
To set the new V
TRIP
voltage, apply the desired V
TRIP
threshold voltage to the V
CC
pin and tie the RESET pin
to the programming voltage V
P
. Then write data 00h to
address 01h. The stop bit following a valid write opera-
tion initiates the V
TRIP
programming sequence. Bring
RESET to V
CC
to complete the operation.
Note:
this
operation may take up to 10 milliseconds to complete
and also writes 00h to address 01h of the EEPROM
array.
Figure 5. Set V
TRIP
Level Sequence (V
CC
= desired V
TRIP
value)
RESET
V
CC
0 1 2 3 4 5 6 7
SCL
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
V
P
= 15V
V
CC
SDA
AEh
Note:
BP0, BP1, BP2 must be disabled.
00h
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
REV 1.1.20 1/13/03
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
Characteristics subject to change without notice.
www.xicor.com
9 of 28
XICOR [ XICOR INC. ]
