stled325 STMicroelectronics, stled325 Datasheet - Page 28

• 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
28/62
Figure 10. Power sense circuit
For the STLED325 itself, there is the normal operational mode where the supply is from the
5 V V
from the V
To conserve power and maintain long battery life in this battery supply mode, only the RTC
and the clock to the RTC remain operational.
1.
So, it means that the system will only switch to battery mode when Vcc drop below 3.5V and
Battery voltage is higher V
2.
It means that the system will switch back to Vcc mode as soon as the V
Vbat.
The STLED325 continually monitors Vcc for an out-of-tolerance condition. Should V
below the Switchover voltage (V
to the device will not be recognized at this time to prevent any erroneous data or outcome
from device. The device also automatically switches over to the battery and powers down
into an ultra low current mode of operation to maximize the super-cap or battery duration. As
system power returns and V
and the power supply is switched to the external V
up mode, the clock registers of RTC are maintained by the attached battery or super-cap.
On power-up, when V
to timing diagram in later part of spec).
Upon power-up, the device switches from battery to V
above Vbat, it will recognize the inputs.
The system will only go into battery mode while:
Vcc < 3.5 V and Vcc < Vbat.
The system will enter back into Vcc mode from battery mode while:
V
CC
CC
. When the V
> V
CC
bat
to the battery or super-cap supply.
CC
CC
drops below a pre-defined low level, the supply source is switched
returns to a nominal value, write protection continues for t
CC
CC
voltage.
Doc ID 17576 Rev 1
rises above Vbat, the battery or super-cap is disconnected
SO
= 3.5 V), the device goes into a low-power mode. Inputs
CC
. During the battery or super-cap back-
CC
when V
CC
> Vbat. When V
CC
is higher than
STLED325
REC
CC
CC
(refer
rises
fall