23
FN6370.3
August 18, 2008
VBAT, then the device will enter Battery Backup Mode and
the I2C interface will be disabled, minimizing VBAT current
drain.
Mode D - This mode combines Legacy Mode battery
switchover with no I2C operation in Battery Backup Mode.
When the VDD voltage drops below VBAT, the device will
enter Battery Backup Mode and the I2C interface will be
disabled, minimizing VBAT current drain.
Note that the IRQ/FOUT 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
need to go to VBAT, and thus battery mode current draw will
increase accordingly.
TABLE 8.
MODE
SBIB BIT
BSW BIT
VBAT
SWITCHOVER
VOLTAGE
I2C ACTIVE IN
BATTERY
BACKUP?
EE PROM
WRITE/READ
IN BATTERY
BACKUP?
FREQ/IRQ
ACTIVE?
NOTES
A
0
Standard Mode,
VTRIP = 2.2V typ
Yes
NO
YES, needs
pull-up to VBAT
VBAT switchover at lower of VBAT or
VTRIP. Pull-ups needed on I
2C to
VBAT to operate in Battery Backup.
B (X1226
Mode)
0
1
Legacy Mode,
VDD < VBAT
Yes
NO
YES, needs
pull-up to VBAT
VBAT switchover at <VDD. Pull-ups
needed on I2C to VBAT to operate in
Battery Backup.
C
1
0
Standard Mode,
VTRIP = 2.2V typ
NO
YES, needs
pull-up to VBAT
VBAT switchover at lower of VBAT or
VTRIP.
D
1
Legacy Mode,
VDD < VBAT
NO
YES, needs
pull-up to VBAT
VBAT switchover at <VDD.
ISL12024