LISA-U series - System Integration Manual
UBX-13001118 - R17
Advance information
System description
Page 39 of 190
1.6
System functions
1.6.1
Module power-on
When the LISA-U series modules are in the not-powered mode (i.e. switched off with the
VCC
module supply
not applied), they can be switched on by:
Rising edge on the
VCC
pin to a valid voltage as module supply (i.e. applying module supply)
Alternately, the
RESET_N
pin can be held to the low level during the
VCC
rising edge, so that the module
switches on releasing the
RESET_N
pin when the
VCC
module supply voltage stabilizes at its proper nominal
value within the normal operating range
The status of the
PWR_ON
input pin of LISA-U series modules while applying the
VCC
module supply is not
relevant: during this phase the
PWR_ON
pin can be set high or low by the external circuit.
When the LISA-U series modules are in the power-off mode (i.e. switched off by means of the AT+CPWROFF
command, with valid
VCC
module supply applied), they can be switched on by:
Low pulse on the
PWR_ON
pin (i.e. forcing to the low level the pin normally high by external pull-up)
Rising edge on the
RESET_N
pin (i.e. releasing from low level the pin, normally high by internal pull-up)
RTC alarm (i.e. pre-programmed scheduled time by AT+CALA command)
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 17: 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, close to accessible point.
1.6.1.1
Rising edge on VCC
Applying a proper supply 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
normal
operating range minimum limit starting from a voltage value lower than 2.25 V (see
LISA-U1 series Data
Sheet
[1] and
LISA-U2 series Data Sheet
[2] for the
VCC
normal operating range minimum limit).
The voltage at
VCC
pins must ramp from 2.5 V to 3.2 V within 1 ms to properly switch on the module.
If the external supply circuit is not able to provide this
VCC
voltage slope, keep the
RESET_N
input low
during the
VCC
rising edge, so that the module switches on, releasing the
RESET_N
pin when the
VCC
voltage stabilizes at its nominal value within the normal operating range.
The status of the
PWR_ON
input pin during the
VCC
apply phase is not relevant: LISA-U modules switch on
when a proper rising edge on the
VCC
pin is applied, during this phase the
PWR_ON
pin can be set high or low
by the external circuit.
