Normal and extreme voltages
Energy management is mainly carried out in the EM ASIC (N2200), which contains a number of regulators. In
addition, there are also some external regulators.
In the table below normal and extreme voltages are shown when a BL-4U battery is used.
Table 9 Nominal voltages
Voltage
Voltage [V]
Condition
General conditions
Nominal voltage
3.7
Lower extreme voltage
3.5
Higher extreme voltage
4.1
(fast charging)
HW shutdown voltages
Vmstr+
2.1 ± 0.1
Off to on
Vmstr-
1.9 ± 0.1
On to off
SW shutdown voltages
Sw shutdown
3.1
In call
Sw shutdown
3.25
In idle
Min operating voltages
Vcoff+
2.9 ± 0.1
Off to on
Vcoff-
2.7 ± 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 and the system is powered down with the aid
of SW. The power key is connected to EM ASIC (N2200) via the PWRONX signal.
The PWRONX line cannot be detected when SW hangs. For that reason, the user has to remove the battery.
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.
RM-750
System Module
Issue 1
COMPANY CONFIDENTIAL
Page 6 – 11
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