Voltage Voltage [V] Condition
Higher extreme voltage
4.2(fast charging)
SW Shutdown Voltages
Sw shutdown 3.3
The PM8921 PMIC determines the system bootup (or shutdown) by comparing the battery voltage with the
UVLO thresholds.
Table 9 UVLO performance specifications
Parameter Comments Min Typ Max Units
Threshold voltage, falling Programmable value 1.500 2.700 3.050 V
Threshold voltage accuracy -5 - +5 %
Hysteresis 100 175 250 mV
UVLO detection interval - 1.0 - µs
The hysteresis acts the following way:
•
For rising threshold (during power up), the threshold would be 2700 + 175 mV
•
For falling threshold (to determine shutdown), the threshold would be 2700 mV
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 and the system is powered down with the aid
of SW. The power key is connected to EM ASIC (N2200) via the KYPD_PWR_N signal.
Modes of operation
Mode Description
NO_SUPPLY (Dead) mode means that the main battery is not present or its voltage is too low (below
N2200 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 is adequate
and the 32 kHz oscillator is running.
PWR_OFF In this mode (warm), the main battery is present and its voltage is over N2200 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 32 kHz clock to count
the RESET 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-824; RM-825; RM-826
System Module
Page 6 – 10 NOKIA INTERNAL USE ONLY Issue 2
Copyright © 2012 Nokia. All rights reserved.
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