LARA-R2 series - System Integration Manual
UBX-16010573 - R02
Objective Specification
Design-in
Page 82 of 148
2.3
System functions interfaces
2.3.1
Module power-on (PWR_ON)
2.3.1.1
Guidelines for PWR_ON circuit design
LARA-R2 series modules’
PWR_ON
input is equipped with an internal active pull-up resistor to the
VCC
module
supply as described in Figure 37: 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 37 and Table 29.
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 accessible point.
An open drain or open collector output is suitable to drive the
PWR_ON
input from an application processor, as
the pin is equipped with an internal active pull-up resistor to the
V_BCKP
supply, as described in Figure 37.
A compatible push-pull output of an application processor can also be used. In any case, take care to set the
proper level in all the possible scenarios to avoid an inappropriate module switch-on.
LARA-R2 series
2
V_BCKP
15
PWR_ON
Power-on
push button
ESD
Open
Drain
Output
Application
Processor
LARA-R2 series
2
V_BCKP
15
PWR_ON
TP
TP
10 k
10 k
Figure 37: 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 29: Example of pull-up resistor and ESD protection 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
accessible testpoint 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 the
LARA-R2 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.
