X1227 View Datasheet(PDF) - Xicor -> Intersil
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X1227 Datasheet PDF : 28 Pages
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X1227
Figure 4. Power On Reset and Low Voltage Reset
VTRIP
VCC
tPURST
tR
RESET
tRPD
tPURST
tF
VRVALID
VCC THRESHOLD RESET PROCEDURE
[OPTIONAL]
The X1227 is shipped with a standard VCC threshold
(VTRIP) voltage. This value will not change over normal
operating and storage conditions. However, in applica-
tions where the standard VTRIP is not exactly right, or if
higher precision is needed in the VTRIP 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 VTRIP Voltage
It is necessary to reset the trip point before setting the
new value.
To set the new VTRIP voltage, apply the desired VTRIP
threshold voltage to the VCC pin and tie the RESET pin
to the programming voltage VP. Then write data 00h to
address 01h. The stop bit following a valid write opera-
tion initiates the VTRIP programming sequence. Bring
RESET to VCC 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 VTRIP Level Sequence (VCC = desired VTRIP value)
RESET
VCC
SCL
0 1 23 4 56 7
VP = 15V
01 23 4 56 7
01 23 4 56 7
VCC
01 23 4 56 7
SDA
AEh
00h
01h
00h
Note: BP0, BP1, BP2 must be disabled.
Resetting the VTRIP Voltage
This procedure is used to set the VTRIP to a “native”
voltage level. For example, if the current VTRIP is 4.4V
and the new VTRIP must be 4.0V, then the VTRIP must
be reset. When VTRIP is reset, the new VTRIP is some-
thing less than 1.7V. This procedure must be used to
set the voltage to a lower value.
To reset the new VTRIP voltage, apply more than 5.5V
to the VCC pin and tie the RESET pin to the
programming voltage VP. Then write 00h to address
03h. The stop bit of a valid write operation initiates the
VTRIP programming sequence. Bring RESET to VCC to
complete the operation. Note: this operation takes up
to 10 milliseconds to complete and also writes 00h to
address 03h of the EEPROM array.
For best accuracy in setting VTRIP, it is advised that the
following sequence be used.
1.Program VTRIP as above.
2.Measure resulting VTRIP by measuring the VCC
value where a RESET occurs. Calculate Delta =
(Desired – Measured) VTRIP value.
3.Perform a VTRIP program using the following formula
to set the voltage of the RESET pin:
VRESET = (Desired Value – Delta) + 0.025V
REV 1.1.20 1/13/03
www.xicor.com
Characteristics subject to change without notice. 9 of 28
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