V1.00 Page 32 of 49 ICM MP CCQ GRM
S55/S57 Company Confidential © Copyright Siemens AG 12/02
6.1.4 Power Supply Functions:
- Power on Reset
To guarantee a defined startup, the ASIC will be reset by a Power on Reset block.
After Power on Reset the ASIC will enter the power done Mode. If the thresholds will
be reached during operating mode the reset will become the device enters the power
down mode. This blocks are always active and will be supplied by VDDREF.
- Switch on and watchdog
There are 3 different possibilities to switch on the phone via external pins:
-VDD_CHARGE with rising edge
-ON/OFF with falling edge
-ON/OFF2 with rising edge
In order to guarantee a defined start-up behavior of the external components, a
sequential power up is used and the correct start up of blocks is supervised. In normal
mode, a continues watchdog signal from the µC is needed to keep the system
running. If this signals fails, the ASIC will switch to power down mode.
It must be guaranteed, that each start up condition does not interfere and block the
other possible start up signals. In case of failure during start up, the device will go
back to power down mode. To guarantee that the connection of the a charging unit
with a very low battery is detected, this detection must work level sensitive at the end
of POR signal.
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