FLY SP-770, As Manual

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input/output. The clock and reset inputs to SIM cards are level shifted from the supply
of digital IO (Vio) of baseband chipset to the SIM supply (Vsim). The bi-directional data
bus is internal pull high with 20kohm resistor on the controller side and with 10kohm
resistor on the SIM side. All pins that connect to the SIM card (Vsim, SRST, SCLK, SIO)
withstand over 5kV of human body mode ESD. In order to ensure proper ESD
protection, careful board layout is required.
3.4.11 Vibrator, Alerter, LED Switches
Three built-in open-drain output switches drive the vibrator motor, alerter beeper and
LEDs in the handset. Each switch is controlled by baseband chipset with enable pins.
The switch of LED can sink 150mA to drive up to 10 LEDs simultaneously for backlight.
The switch of vibrator can sink 250mA for a vibrator motor. The switch of alerter can
sink 300mA to drive the beeper. And all the open-drain output switches are high
impedance when disable.
3.5 Power Sequence and Protection Logic
The MT6305 handles the powering ON and OFF of the handset. It is possible to start the
power on sequence in three different ways:
-Pulling PWRKEY low
-Pulling PWRBB high
-CHRIN exceeds Chr Det threshold
Pulling PWRKEY low is the normal way of turning on the handset. This will turn on Vcore,
Vio, Vm LDOs as long as the PWRKEY is held low. The Vtcxo and Va LDOs is turned on
when SRCLKEN is high. The microprocessor then starts and pulls PWRBB high after
which PWRKEY can be released. Pulling PWRBB high will also turn on the handset. This
is the case when the alarm in the RTC expires.
Applying an external supply on CHRIN will also turn the handset on. If MT6305 is in the
UVLO state, applying the adapter will not start up the LDOs.
3.5.1 Under voltage Lockout (UVLO)
The UVLO function in the MT6305 prevents startup when initial voltage of the main
battery is below the 3.2V threshold. When the battery voltage is greater than 3.2V,
the UVLO comparator trips and the threshold is reduced to 2.9V. This allows the
handset to start normally until the battery decays to below 2.9V. Once the MT6305
enters UVLO state, it draws very low quiescent current, typically 30µA. The RTC LDO
is still running until the DDLO disables it. In this mode the MT6305 draws 5µA of
quiescent current.
3.5.2 Deep Discharge Lockout (DDLO)
The DDLO in the MT6305 has two functions:
-To turn off the Vrtc LDO.
-To shut down the handset when the software fails to turn off the phone when the
battery drops below 3.0V. The DDLO will shut down the handset when the battery
falls below 2.5 V to prevent further discharge and damage to the cells.