Integration Manual

Table Of Contents
TOBY-L3 series - System Integration Manual
TSD-19090601 - R13 System Integration Manual Page 77 of 143
2.3 System functions interfaces
2.3.1 Module power-on (PWR_ON)
2.3.1.1 Guidelines for PWR_ON circuit design
TOBY-L3 series PWR_ON input is equipped with an internal active pull-up resistor to an internal 1.3 V
supply rail as shown in Figure 29: 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 shown in Figure 29 and Table 24.
The ESD sensitivity rating of the PWR_ON pin is 1 kV (HBM according to JESD22-A114). A 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 the 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 the pin is equipped with an internal active pull-up resistor, as shown in Figure 29.
TOBY-L3 series
20
PWR_ON
Power-on
push button
ESD
Open
Drain
Output
Application
Processor
TOBY-L3 series
200 k
20
PWR_ON
TP
TP
200 k
VCC_INT
VCC_INT
Figure 29: PWR_ON application circuits using a push button and an open drain output of an application processor
Reference
Description
Part Number - Manufacturer
ESD
CT0402S14AHSG - EPCOS
Varistor array for ESD protection
Table 24: 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, for diagnostic purposes.