Integration Manual
SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R13 Design-in Page 56 of 119
2.3 System functions interfaces
2.3.1 Module power-on (PWR_ON)
2.3.1.1 Guidelines for PWR_ON circuit design
SARA-R4/N4 series PWR_ON input is equipped with an internal active pull-up resistor; an external pull-up resistor is not
required and should not be provided.
If connecting the PWR_ON input to a push button, the pin will be externally accessible on the application device.
According to EMC/ESD requirements of the application, an additional ESD protection should be provided close to the
accessible point, as described in Figure 29 and Table 20.
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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, and it can be achieved by mounting an ESD protection (e.g. EPCOS
CA05P4S14THSG varistor) close to the accessible point.
An open drain or open collector output is suitable to drive the PWR_ON input from an application processor, as described
in Figure 29.
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PWR_ON input pin should not be driven high by an external device, as it may cause start up issues.
SARA-R4/ N4
15
PW R_ON
Power-on
push butt on
ESD
Open
Drain
Out put
Applicat ion
Processor
SARA-R4/ N4
15
PW R_ON
TP
TP
Figure 29: PWR_ON application circuits using a push button and an open drain output of an application processor
Reference Description Remarks
ESD CT0402S14AHSG - EPCOS Varistor array for ESD protection
Table 20: Example ESD protection component for the PWR_ON application circuit
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It is recommended to provide direct access to the PWR_ON pin on the application board by means of an accessible
test point directly connected to the PWR_ON pin.
2.3.1.2 Guidelines for PWR_ON layout design
The power-on circuit (PWR_ON) requires careful layout since it is the sensitive input available to switch on and switch off
the SARA-R4/N4 series modules. It is required to 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.