Power Key And System Power-Up - Nokia 2608 Service Manual

Power key and system power-up

The QSC6020 controls the power up and reset. The baseband can power up in the following w
Pressing the Power button, which means to ground the KPD_PWR_N ("KPD_PWR_N" pin in 2608 schematic
pin of the QSC6020
Connecting the charger to the charger input.
Afte r receiving o ne of the above signals, the PM will start to enter reset mode. The watchdog starts, and if the
batt ery volta ge is greater than its threshold (3V), a 6ms delay starts to allow MSM to settle. After this delay
ela pses, the VERG_MSMC r
in s equence after MSMC. There is a 120us (4 Slee
PON_RESET_N ("RESIN_N" pin in 2608 schematic) line holds low for another 20ms and is sent to MSM. Resets are
generated for the MSM's internal MCU and its internal DSP, and MSM sends TCXO_ON ("TCXO_EN" pin in 2608
schematic) signal to PM to enable TCXO. After PON_RESET_N goes high, MSM holds PS_HOLD at low state for
200m s and then drives PS_HOLD to high state. This will keep all regulators at on state in order to complete
this power on sequence. KPD_PWR_N key can be released a
The RESOUT_N fro m QSC6020 is use to reset
power d own during sleep mode.
baseb and re gulators a
resets during normal oper
Then, QSC6020 drives RESOUT_N
repre sents th e PM star
The mobile terminal can use the power key or a charger to power up.
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egulator enables. Then, VERG_MSMP, VERG_MSMA & VERG_TCXO regulators are enabled
d
LC D_RS from
re switch ed on w hen t
ation. If the watch
and LCD_R
t-up sequ ence fr om rese o power-on.
Figure 6 Power-on/Power-off sequence and timing
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p_Clocks) delays between each regulator's turn on. The
fter PS_HOLD goes high.
fla sh mem ory during power up and to put the flash memory in
QSC6020 is used to reset LCD module during power up. All
he PM is powered on. The QSC6020s internal watch
do g expires, it will generate a reset signal to reset to MSM sta
S low to reset flash memory
t t
System Module and User Interface
and LCD module. Below figure
RM-376
ays:
)
dog runs and
tus.
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