Voltage Voltage [V] Condition
Vcoff- 2.6 ± 0.1 On to off
Power key and system power-up
When the battery is placed in the phone the power key circuits are energized. When the power key is pressed,
the system boots up (if an adequate battery voltage is present).
Power down can be initiated by pressing the power key again (the system is powered down with the aid of
SW). The power key is connected to RETU ASIC via PWRONX signal.
Different power-up conditions
Power up can be caused by the following reasons:
• Power key is pressed
• Charger is connected
• RTC alarm occurs
• MBUS wake-up
After that:
• RETU activates sleep clock and VANA, VDRAM, VIO and VR1 regulators.
• Voltage appearing at RETU’s RSTX pin is used for enabling TAHVO ASIC.
• TAHVO enables VCORE regulator and its internal RC-oscillator (600kHz).
• VCTCXO regulator is set ON and RF clock (main system clock) is started to produce.
• RETU will release PURX ~ 16ms after power up is enabled (the RF clock is then stable enough).
• Synchronizing clock (2.4MHz) for TAHVO is started to be produced. After PURX is released and two rising
edges of 2.4MHz synchronous clock have been detected in SMPSClk input TAHVO is starting to use that
instead of 600kHz internal RC-oscillator.
• HW start-up procedure has been finalized and the system is up and running. Now it is possible for SW to
switch ON other needed regulators.
Modes of operation
Mode Description
NO_SUPPLY (dead) mode means that the main battery is not present or its voltage is too low (below
RETU master reset threshold) and that the back-up battery voltage is too low.
BACK_UP The main battery is not present or its voltage is too low but back-up battery voltage is
adequate and the 32kHz oscillator is running (RTC is on).
PWR_OFF In this mode (warm), the main battery is present and its voltage is over RETU master
reset threshold. All regulators are disabled, PurX is on low state, the RTC is on and the
oscillator is on. PWR_OFF (cold) mode is almost the same as PWR_OFF (warm), but the
RTC and the oscillator are off.
RESET RESET mode is a synonym for start-up sequence. RESET mode uses 32kHz clock to count
the REST mode delay (typically 16ms).
SLEEP SLEEP mode is entered only from PWR_ON mode with the aid of SW when the system’s
activity is low.
FLASHING FLASHING mode is for SW downloading.
RM-123; RM-145
Nokia Customer Care System Module
Page 8 –8 COMPANY CONFIDENTIAL Issue 1
Copyright © 2006 Nokia. All rights reserved.
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