Ublox SARA-N2 Series, System Integration Manual

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SARA-N2 / N3 series - System integration manual
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2.3 System functions interfaces
2.3.1 Module power-on (PWR_ON)
2.3.1.1 Guidelines for PWR_ON circuit design
☞
The PWR_ON input pin is not available in SARA-N2 series modules.
As described in SARA-N3 series data sheet [2] , the module has an internal pull-up resistor on the
PWR_ON input line, so an external pull-up is not required on the application board.
When the PWR_ON input is connected to a push button that shorts the PWR_ON input pin to ground,
the pin will be externally accessible on the application device. According to EMC/ESD requirements of
the application, provide an additional ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) on
the line connected to this pin, close to an accessible point, as described in
Figure 20 and Table 14 .
☞
The ESD sensitivity rating of the PWR_ON pin is 1 kV (Human Body Model according to JESD22-
A114). Higher protection level can be required if the line is externally accessible on the application
board, e.g. if an accessible push button is directly connected to
PWR_ON pin. Higher protection
level can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array)
close to the accessible point.
When the PWR_ON input is connected to an external device (e.g. application processor), an open drain
output can be directly connected without any external pull-up, as described in Figure 20 and Table 14 .
The internal pull-up resistor provided by the module pulls the line to the high logic level when the
application processor does not force the
PWR_ON pin low.
SARA-N3 series
15
PWR_ON
Power-on
push button
ESD
Open
drain
output
Application
processor
SARA-N3 series
15
PWR_ON
TP TP
1.1 V
1.1 V
Figure 20: PWR_ON application circuits using a push button and an open drain output of an application processor
Reference Description Part number - Manufacturer
ESD Varistor for ESD protection B72590T8140S160 - TDK
Table 14: Example of ESD protection component for the PWR_ON application circuit
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It is recommended to provide on the application board a directly accessible Test-Point connected
to the
PWR_ON pin for diagnostic purpose.
2.3.1.2 Guidelines for PWR_ON layout design
The power-on circuit ( PWR_ON ) requires careful layout due to the pin function: ensure that the
voltage level is well defined during operation and no transient noise is coupled on this line; otherwise
the module might detect a spurious power-on request.