ISL12024IRTC Datasheet, PDF (23/24 Pages) Intersil Corporation – Real-Time Clock/Calendar

ISL12024IRTC
Note that the status register AL0 bit will be set each time the
battery, then the ISL12024IRTCZ can communicate in
alarm is triggered, but does not need to be read or cleared.
I²C Communications During Battery Backup
Battery Backup Mode. This mode places the
ISL12024IRTCZ device in the same operating mode as
the X1226 legacy device.
Operation in Battery Backup Mode is affected by the BSW
and SBIB bits as described earlier. These bits allow flexible
operation of the serial bus and EEPROM in Battery Backup
Mode, but certain operational details need to be clear before
utilizing the different modes. Table 8 describes four different
modes possible with using the BSW and SBIB bits, and how
• Mode C - This mode combines Standard Mode battery
switchover with no I²C operation in Battery Backup Mode.
When the V_DD voltage drops below the lower of V_TRIP or
tVh^Be^AI^{T2,CthienntetrhfaecdeewviilclebewdilliseanbtelerdB, amttienrimy BizaincgkuVp}_BA^M_T^{ocduerraenndt}
drain.
they affect the serial interface and battery backup operation.
• Mode A - In this mode, selection bits indicate a Standard
Mode switchover combined with I²C operation in Battery
Backup Mode. When the V_DD voltage drops below the
lower of V_TRIP or V_BAT, then the device will enter Battery
Backup Mode. If the microcontroller and bus pull-ups are
also powered by the battery, then the ISL12024IRTCZ can
communicate in Battery Backup Mode.
• Mode D - This mode combines Legacy Mode battery
switchover with no I²C operation in Battery Backup Mode.
When the V_DD voltage drops below
enter Battery Backup Mode and the
VI_{2BCATin, ttehrefadceevwiciell}
will
be
disabled, minimizing V_BAT current drain.
Note that the IRQ/F_OUT open drain output pin is active in
battery backup for all modes, allowing clocking of devices
while in Battery Backup Mode. The pull-up on the pin will
• Mode B - In this mode selection, bits indicate Legacy
Mode switchover combined with I²C operation in Battery
need to go to V_BAT, and thus battery mode current draw will
increase accordingly.
Backup Mode. When the V_DD voltage drops below V_BAT,
the device will enter Battery Backup Mode. If the
microcontroller and bus pull-ups are also powered by the
TABLE 8.
MODE
SBIB BIT
BSW BIT
V_BAT
SWITCHOVER
VOLTAGE
EEPROM
I²C ACTIVE IN WRITE/READ
BATTERY IN BATTERY
BACKUP? BACKUP?
FREQ/IRQ
ACTIVE?
NOTES
A
0
B (X1226
0
Mode)
0
Standard Mode,
Yes
V_TRIP = 2.2V typ
1
Legacy Mode,
Yes
V_DD < V_BAT
NO
YES, needs
pull-up to V_BAT
VV^BTRATIP.swPuitcll-huopvserneaet dloewdeornofI^2VCBAto^{T or}
V_BAT to operate in Battery Backup.
NO
YES, needs
pull-up to V_BAT
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Battery Backup.
C
1
0
Standard Mode,
NO
V_TRIP = 2.2V typ
D
1
1
Legacy Mode,
NO
V_DD < V_BAT
NO
YES, needs V_BAT switchover at lower of V_BAT or
pull-up to V_BAT V_TRIP.
NO
YES, needs V_BAT switchover at <V_DD.
pull-up to V_BAT
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FN6749.1
December 15, 2011