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5.15.3. Power ON/OFF Control
The power on sequence can begin when VBAT > 2.8 V or VBACKUP > 2.8 V. In this state IOTA (U8) is in Power
On Condition and internal supply UPR is active. RESPWRONZ signal to G2_Lite (U3) is released high.
If IOTA is in the Power On Condition, one of following conditions starts the Power Up sequence.
8 Power key is pushed for more than 30 ms.
8 RPWON input goes high to low for more than 30 ms (e.g. accessory is connected or external RTC signal is activated).
8 EXTPWR voltage is higher than (VBAT+0.4) V.
8 G2_Lite RTC ALARM signal goes high.
The Power Up sequence is as follows:
1. Local Oscillator OSCAS is started (if not already active for debouche operation).
2. IOTA internal band gap reference is activated.
3. If VBAT < 3.2 V after a timeout of 51.2 ms OSCAS is stopped and Power Up sequence is aborted.
4. Charge pump is enabled.
5. All regulators are enabled.
6. Power Up status bit and internal Reset bits are set.
7. ONnOFF signal is set to activate G2_Lite.
8. ARM in G2_Lite starts running software using 32 kHz clock, and also starts 13 MHz clock.
The following Power Down sequence can only be started by G2_Lite setting the DEVICE_OFF bit in IOTA or, in emergency
case, when VBAT < 2.7 V (or VBAT < Vbackup & VBAT < 2.8 V):
1. If emergency case INT1 is set low by IOTA.
2. IOTA starts an internal 150 µs watchdog timer to allow G2_Lite to shutdown.
3. ONNOFF signal is reset to deactivate G2.
4. All regulators are disabled.
5. IOTA internal band gap reference is deactivated.
6. OSCAS is stopped.
5.15.4. Voltage Regulation
Each power source is specified as follows.
8 VRDBB: Power supply for G2_Lite
Voltage 1.5 V
Current 120 mA max
Dropout 100 mV max (load max)
8 VRRAM: Power supply for SRAM and G2_Lite
Voltage 2.8 V
Current 50 mA max
Dropout 100 mV max (load max)
8 VRMEM: Power supply for flash memory, LCD and G2_Lite
Voltage 2.8 V
Current 60 mA max
Dropout 100 mV max (load max)
8 VRIO: Power supply for Melody and G2_Lite
Voltage 2.8 V
Current 100 mA max
Dropout 100 mV max (load max)
8 VRABB: Power supply for G2_Lite
Voltage 2.8 V
Current 50 mA max
Dropout 100 mV max (load max)
8 VRSIM: Power supply for SIM
Voltage 2.85 V
Current 10 mA max
Dropout 100 mV max (load max)
– 5-12 –
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