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LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
System description
Page 33 of 125
1.6.1.1
Rising edge on VCC
When a supply is connected to
VCC
pin, the module supply supervision circuit controls the subsequent activation
of the power up state machines: the module is switched-on when the voltage rises up to the
VCC
normal
operating range minimum limit (3.35 V) starting from a voltage value lower than 2.25 V.
1.6.1.2
Low level on the PWR_ON
Power-on sequence of the module starts when a low level is forced on the
PWR_ON
signal for at least 5 ms.
The electrical characteristics of the
PWR_ON
input pin are different from the other digital I/O interfaces: the high
and the low logic levels have different operating ranges and the pin is tolerant against voltages up to the battery
voltage. The detailed electrical characteristics are described in
LEON-G100 / LEON-G200
Data Sheet
PWR_ON
pin has high input impedance and is weakly pulled to the high level on the module. Avoid
keep it floating in noisy environment. To hold the high logic level stable, the
PWR_ON
pin must be
connected to a pull-up resistor (e.g. 100 k
Ω
) biased by the
V_BCKP
supply pin of the module.
If
PWR_ON
input is connected to a push button that shorts the
PWR_ON
pin to ground, the
V_BCKP
supply pin
of the module can be used to bias the pull-up resistor.
If
PWR_ON
input is connected to an external device (e.g. application processor), it is suggested to use an open
drain output of the external device with an external pull-up. Connect the pull-up the
V_BCKP
supply pin of the
module.
If
PWR_ON
pin is connected to a push-pull output pin of an application processor, the pull-up can be provided
to pull high the
PWR_ON
level when the application processor is switched off. If the high-level voltage of the
push-pull output pin of the application processor is greater than 2.0 V, the
V_BCKP
supply cannot be used to
bias the pull-up resistor: the supply rail of the application processor, or the
VCC
supply could be used but this
will increase the
V_BCKP
(RTC supply) current consumption when the module is in not-powered mode (i.e.
VCC
supply not present). Using a push-pull output of the external device, take care to fix the proper level in all the
possible scenarios to avoid an inappropriate switch-on of the module.
The module can be switched-on by forcing a low level for at least 5 ms on the
PWR_ON
pin: the
module is not switched-on by a falling edge provided on the
PWR_ON
pin. The suggested
PWR_ON
pull-up resistor value is 100 k
Ω
: lower resistance value will increase the module power-off consumption.
The suggested supply to bias the pull-up resistor is the
V_BCKP
supply pin of the module.