Siemens SL55 - Power Supply Functions

Customer Care
V 1.0 Page 31of 52 ICM MP CCQ GRM
SL55
Company Confidential © Copyright Siemens AG
06/03
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.