LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 32 of 125
V_INT
can only be used as an output; don’t connect any external regulator on
V_INT
. If not used, this
pin should be left unconnected.
The
V_INT
digital interfaces supply output is mainly used to:
Pull-up DDC (I
2
C) interface signals (see section 1.10 for more details)
Pull-up SIM detection signal (see section 1.8 for more details)
Indicate when the module is switched on and the
RESET_N
(external reset input pin) is not forced to the low
level
1.6
System functions
1.6.1
Module power on
The module power on sequence is initiated in one of these ways:
Rising edge on the
VCC
pin to a valid voltage for module supply
Falling edge on the
PWR_ON
pin
Rising edge on the
RESET_N
pin
RTC alarm
Name
Description
Remarks
PWR_ON
Power on input
PWR_ON
pin has high input impedance.
Do not keep floating in noisy environment: external pull-up
required.
Table 11: Power on pin
The
PWR_ON
pin ESD sensitivity rating is 1 kV (Human Body Model according to JESD22-A114F). Higher
protection level could be required if the line is externally accessible on the application board. Higher
protection level can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor
array) on the line connected to this pin.
1.6.1.1
Rising edge on VCC
When a supply is connected to
VCC
pins, 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
operating range minimum limit (3.4 V) starting from a voltage value lower than 2.25 V (See
LISA-U1 series
Data
Sheet
The voltage at the
VCC
pins must ramp from 2.5 V to 3.2 V within 1 ms to switch on the module.
1.6.1.2
Falling edge on PWR_ON
The module power on sequence starts when a falling edge is forced on the
PWR_ON
input pin. After applying a
falling edge, it is suggested to hold a low level on the
PWR_ON
signal for at least 5 ms to properly switch on the
module.
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 to voltages up to the battery
voltage. The detailed electrical characteristics are described in the
LISA-U1 series Data Sheet
