Ublox MPCI-L1 series, Руководство по системной интеграции

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TOBY-L1 and MPCI-L1 series - System Integration Manual
UBX-13001482 - R04 Advance Information Design-in
Page 46 of 90
2.3 System functions interfaces
2.3.1 Module power-on (PWR_ON)
The PWR_ON input pin is not accessible on MPCI-L1 series modules.
2.3.1.1 Guidelines for PWR_ON circuit design
Pull-up resistor (e.g. 100 k
Ω
) biased by the
V_BCKP
supply pin of the module should be implemented as
described in Figure 24 and Table 15. 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 (e.g. EPCOS CA05P4S14THSG varistor array) should be implemented at close to
accessible point on the line connected to this pin.
The PWR_ON pin has high input impedance and is weakly pulled to the high level on the module. Avoid
keeping it floating in a noisy environment. To hold the high logic level stable, the PWR_ON pin must be
connected to a pull-up resistor (e.g. 100 k
Ω
) biased by the V_BCKP supply pin of the module.
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.
Using an open drain output from a host to connect the
PWR_ON input to an application processor in couple
with an external pull-up resistor (e.g. 100 k
Ω
) biased by the V_BCKP supply pin of the module, as described in
Figure 24 and Table 15.
A compatible push-pull output of an application processor can also be used. In this case the pull-up can be
provided to pull the
PWR_ON
level high when the application processor is switched off. If the high-level voltage
of the push-pull output pin of the application processor is greater than the voltage of the V_BCKP pin (refer to
TOBY-L1 series Data Sheet [1]), the V_BCKP supply cannot be used to bias the pull-up resistor. The supply rail of
the application processor or the module VCC supply could be used. Using a push-pull output of the external
device, take care to fix the proper level in all the possible scenarios to avoid an inappropriate module switch-on.
TOBY-L1 series
Rext
3
V_BCKP
20
PWR_ON
Power-on
push button
ESD
Open
Drain
Output
Application
Processor
TOBY-L1 series
Rext
3
V_BCKP
20
PWR_ON
TP TP
Figure 24: PWR_ON application circuits using a push button and an open drain output of an application processor
Reference Description Remarks
Rext 100 k
Ω
Resistor 0402 5% 0.1 W External pull-up resistor
ESD CT0402S14AHSG - EPCOS Varistor array for ESD protection
Table 15: 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 an
accessible test point directly connected to the PWR_ON pin.