Power Up With Pwr Key; Power Up When Charger Is Connected - Nokia RH-27 Series Technical Documentation Manual

RH-27
Troubleshooting - Baseband

Power up with PWR key

When the Power on key is pressed, the UEM enters the power up sequence. Pressing the
power key causes the PWRONX pin on the UEM to be grounded. The UEM PWRONX sig-
nal is not part of the keypad matrix. The power key is only connected to the UEM. This
means that when pressing the power key, an interrupt is generated to the UPP that starts
the MCU. The MCU then reads the UEM interrupt register and notices that it is a
PWRONX interrupt. The MCU now reads the status of the PWRONX signal using the UEM
control bus, CBUS. If the PWRONX signal stays low for a certain time, the MCU accepts
this as a valid power on state and continues with the SW initialization of the baseband.
If the power on key does not indicate a valid power on situation the MCU powers off the
baseband.

Power up when charger is connected

In order to be able to detect and start charging in the case where the main battery is
fully discharged (empty) and hence UEM has no supply (NO_SUPPLY or BACKUP mode of
UEM), charging is controlled by START-UP CHARGING circuitry.
Whenever VBAT level is detected to be below master reset threshold (VMSTR-), charging
starts and is controlled by START_UP charge circuitry. Connecting a charger forces
VCHAR input to rise above the charger detection threshold, VCHDET+, and by detection
charging is started. UEM generates 100mA constant output current from the connected
charger's output voltage. As battery charges, its voltage rises and when VBAT voltage
level is detected to be higher than the master reset threshold limit (VMSTR+), START_UP
charge is terminated.
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©2003 Nokia Corporation
CCS Technical Documentation
Confidential Issue 1 11/2003