LENA-R8 series - System integration manual
UBX-22015376 - R02
Design-in
Page 49 of 116
C1-Public
2.3
Cellular system functions interfaces
2.3.1
Cellular power-on (PWR_ON)
2.3.1.1
Guidelines for PWR_ON circuit design
LENA-R8 series
modules’
PWR_ON
input line is internally pulled up as illustrated in
: 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
☞
The ESD sensitivity rating of the
PWR_ON
pin is 1 kV (HBM according to JESD22-A114). Higher
protection level can be required if the line is externally accessible on the application board, as if an
accessible push button is directly connected to the
PWR_ON
pin, and it can be achieved by
mounting an ESD protection (as 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 the pin is internally pulled up as illustrated in
LENA-R8 series
15
PWR_ON
Power-on
push button
ESD
Open
Drain
Output
Application
Processor
LENA-R8 series
15
PWR_ON
TP
TP
Figure 30: PWR_ON application circuits using a push button and an open drain output of an application processor
Reference
Description
Part number - manufacturer
ESD
Varistor array for ESD protection
CT0402S14AHSG - EPCOS
Table 18: 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 Test-Point directly connected to the
PWR_ON
pin, for FW upgrade and for diagnostic purpose.
2.3.1.2
Guidelines for PWR_ON layout design
The
PWR_ON
circuit requires careful layout since it is the sensitive input available to switch on the
cellular system. 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 request.
2.3.2
Cellular reset (RESET_N)
2.3.2.1
Guidelines for RESET_N circuit design
LENA-R8 series
modules’
RESET_N
input line is internally pulled up as illustrated in
: an
external pull-up resistor is not required and should not be provided.
If connecting the
RESET_N
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 device (e.g., the EPCOS CA05P4S14THSG varistor) should be provided close to the
accessible point on the line connected to this pin, as described in
☞
The ESD sensitivity rating of the
RESET_N
pin is 1 kV (HBM according to JESD22-A114). Higher
protection level can be required if the line is externally accessible on the application board, e.g., if
