SARA-R5 series - System integration manual
UBX-19041356 - R04 Design-in Page 53 of 118
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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
SARA-R5 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 30 and Table 16.
☞ 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 30.
☞ PWR_ON input pin should not be driven high by an external device, as it may cause start up issues.
Table 16: 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.
2.3.1.2 Guidelines for PWR_ON layout design
The power-on circuit (PWR_ON) requires careful layout due to the pin function (see sections 1.6.1 and
1.6.2). 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.
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