Panasonic EB-GD93, Technical Manual

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POWER SUPPLIES
Issue 1 Section 9 MCUK001001G8
Revision 0 – 36 – Technical Guide
9.3.3. Power-up Sequence
The power-up sequence can be initiated by pressing the power key, or by applying a power source to the EXT_PWR signal
line. Both enable the linear regulators and the CPU becomes active. The CPU must then check the battery condition; if the
phone is not required to power-down or sleep immediately, the result must be OK or LOW. The CPU then checks to see if a
hands-free unit is connected by polling the nACC_SENSE signal, LOW when HF is connected.
Now the CPU can determine whether to remain powered-up or not, according to the truth-table shown below. In each case the
active parameters are shaded.
With a hands-free unit connected, the phone can be configured via the MMI to power-up and down with transitions of the vehicle
ignition. These are sensed by the CPU on nACC_SENSE.
Any other state than those in the table will cause the phone to deactivate the PSU by setting STAY_ALIVE LOW.
While the CPU is active, it must monitor the battery condition and accessory connectivity and change state accordingly.
9.4. Power-down
There are two power-down procedures:
The truth-table for the power state transitions is shown below. In some cases the phone does not power-down completely but
may enter a state of reduced functionality, e.g. from active to charge mode.
Battery Voltage (V) Temp Reading EXT_PWR Result
X (don't care) invalid <VBAT + 0.4 V Power-down (battery fault)
X invalid >VBAT + 0.4 V Sleep (battery fault)
<3.0 X <VBAT + 0.4 V Power-down (low battery)
<3.5 valid <VBAT + 0.4 V LOW
>3.5 valid X OK
Battery Condition EXT_PWR nACC_SENSE KBR0 ACC_PWR Mode
OK X X 1 1 active
LOW >VBAT + 0.4 V X 1 1 restricted
OK or LOW >VBAT + 0.4 V X 0 1 charge
OK >VBAT + 0.4 V <0.5 V 0 1 active or charge
LOW >VBAT + 0.4 V <0.5 V 0 1 restricted or charge
Current Mode EXT_PWR nACC_SENSE KBR0
Battery
Condition
New Mode
Charge X X 1 OK active
Charge >VBAT + 0.4 V X 1 LOW restricted
Restricted X X 0 OK active
Procedure Description
Normal power-down In this case, the software has full control over the power-down procedure. Calls can be
terminated gracefully etc. In some cases the PSU is not deactivated but there is a
change of operating mode.
Emergency power-down This situation is caused by battery removal and is flagged by FIQ. In this case, the
CPU only has time to perform a subset of the normal procedure. The priority is to pre-
vent corruption of SIM data.