SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11 Design-in Page 76 of 157
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.
☞ 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.
☞ PWR_ON input pin should not be driven high by an external device, as it may cause start up issues.
SARA-R4/N4
15
PWR_ON
Power-on
push but t on
ESD
Open
Drain
Out put
Application
Processor
SARA-R4/N4
15
PWR_ON
TP
TP
Figure 29: PWR_ON application circuits using a push button and an open drain output of an application processor
Varistor array for ESD protection
Table 20: Example ESD protection component for the PWR_ON application circuit
☞ 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.
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