Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R13 System description Page 23 of 119
1.6 System function interfaces
1.6.1 Module power-on
When the SARA-R4/N4 series modules are in the not-powered mode (i.e. the VCC module supply is not applied), they can
be switched on as follows:
• Rising edge on the VCC input pins to a valid voltage level, and then a low logic level needs to be set at the PWR_ON
input pin for a valid time.
When the SARA-R4/N4 series modules are in the power-off mode (i.e. switched off) or in the Power Saving Mode (PSM),
with a valid VCC supply applied, they can be switched on as follows:
• Low pulse on the PWR_ON pin for a valid time period
The PWR_ON input pin is equipped with an internal active pull-up resistor. Detailed electrical characteristics with voltages
and timings are described in the SARA-R4/N4 series Data Sheet [1].
Figure 9 shows the module switch-on sequence from the not-powered mode, with following phases:
• The external power supply is applied to the VCC module pins
• The PWR_ON pin is held low for a valid time
• All the generic digital pins are tri-stated until the switch-on of their supply source (V_INT).
• The internal reset signal is held low: the baseband core and all digital pins are held in reset state. When the internal
reset signal is released, any digital pin is set in the correct sequence from the reset state to the default operational
configured state. The duration of this phase differs within generic digital interfaces and USB interface due to host /
device enumeration timings.
• The module is fully ready to operate after all interfaces are configured.
VCC
PWR_ON
RESET_N
V_INT
Internal Reset
GPIO
System State
BB Pads State
Operational
OFF ON
Internal Reset
→
OperationalTristate / Floating Internal Reset
Start of interface
configuration
Module interfaces
are configured
Start-up
event
~4.5 s0 s
Figure 9: SARA-R4/N4 series switch-on sequence description
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The Internal Reset signal is not available on a module pin, but it is highly recommended to monitor:
o the V_INT pin, to sense the start of the SARA-R4/N4 series module switch-on sequence
o the GPIO pin configured to provide the module operating status indication (see SARA-R4/N4 series Commands
Manual [2], AT+UGPIOC), to sense when the module is ready to operate
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☞ Before the switch-on of the generic digital interface supply (V_INT) of the module, no voltage driven by an external
application should be applied to any generic digital interface of the module.
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☞ Before the SARA-R4/N4 series module is fully ready to operate, the host application processor should not send any
AT command over AT communication interfaces (USB, UART) of the module.
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☞ The duration of the SARA-R4/N4 series modules’ switch-on routine can vary depending on the application / network
settings and the concurrent module activities.
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⚠ An abrupt removal of the VCC supply or forcing a low level on the RESET_N input once the boot of SARA-R4/N4 series
modules has been triggered may lead to an unrecoverable faulty state!