Power Distribution; Power Key - Nokia RM-57 Service Manual

RM-57/58
Nokia Customer Care System Module
The master reset threshold controls the internal reset of Retu / (Tahvo). If battery voltage is above VMSTR,
Tahvo's charging control logic is alive. Also, RTC is active and supplied from the main battery. Above VMSTR,
Tahvo allows the system to be powered on although this may not succeed due to voltage drops during start
up. SW can also consider battery voltage too low for operation and power down the system.

Power key

The system boots up when power key is pressed (adequate battery voltage, VBAT, present).
Power down can be initiated by pressing the power key again (the system is powered down with the aid of
SW). Power on key is connected to Retu ASIC via PWRONX signal.

Power distribution

Figure 96 Power distribution diagram
Power supply components:
• RETU
• TAHVO
• OMAP VCORE SMPS
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