stled325 STMicroelectronics, stled325 Datasheet - Page 30

• Manufacturer Part Number: stled325
• Description: I?c Interfaced, Advanced Led Controller/driver With Keyscan, Standby Power Management And Real Time Clock Rtc
• Manufacturer: STMicroelectronics

Functional description
3.17.2
3.17.3
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spike is very low into the battery. The battery must be protected against such spikes. This is
not relevant for super-cap.
During the switching from V
Battery low warning
The STLED325 automatically performs battery voltage monitoring upon power-up. If the
interrupt for this condition (ABE) is enabled, the RTC will generate an interrupt pulse if the
battery voltage is found to be less than a minimum of 2.5V. However, this condition is
unlikely to go away very quickly as time is needed for the battery to be replaced, and it is not
desirable to keep issuing an interrupt.
Therefore when this bit is set, this condition is checked once every week. If the condition is
still true, then interrupt is sent again.
The ABE bit is an enable bit for battery status check. If the ABE bit was set and the battery
low is generated during a power up sequence, this indicates that the battery is below
approximately 2.5 V and may not be able to maintain data integrity. At this point, a fresh
battery needs to be installed or the super-cap recharged.
This situation only occurs when a battery is used but not with a super-cap as the super-cap
re-charges when the supply is present.
Different power operation modes
The device is capable to support the different power modes as shown in the
Table 8.
Absent (Float or 0V)
Absent (Float or 0V)
V
CC
Present
Present
V
< 3.5V
CC
Different power operation modes
Absent (Float or 0V)
Absent (Float or 0V)
BAT
V
Doc ID 17576 Rev 1
BAT
Present
Present
to V
V
BAT
> V
CC
CC
, the I2C is active after a minimum of 5ms.
V
V
CC
CC
V
V
V
V
Condition
BAT
BAT
CC
CC
> V
< 3.5V and
> V
> 3.5V
> 2.5V
< 2.5V
BAT
BAT
and
Chip does not function.
chip from V
Completely shutdown.
Chip operations from
Chip operations from
Normal operation of
Normal operation of
V
V
mode of operation
mode of operation
BAT
BAT
chip from V
Operation
in a low power
in a low power
Table 8.
is 3.5V
CC until
STLED325
CC
V
CC