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 47 of 90
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
TOBY-L1 series modules, once a valid VCC supply is provided beforehand. For the PWR_ON pin, ensure the
voltage level is well defined during operation and no transient noise is coupled on this line, otherwise the
module might detect an undesirable spurious power-on request.
2.3.2 Module reset (RESET_N and PERST#)
2.3.2.1 Guidelines for RESET_N and PERST# circuit design
As described in Figure 14, the TOBY-L1 and MPCI-L1 series modules have an internal pull-up resistor on the reset
input line: an external pull-up is not required on the application board.
Connecting the
RESET_N
or
PERST#
input to a push button that shorts the
RESET_N
or
PERST#
pin to ground
would make the pin externally accessible on the application device. According to EMC/ESD requirements of the
application, it is required to provide an additional ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) on
the line connected to this pin, close to accessible point, as described in Figure 25 and Table 16.
ESD sensitivity rating of the
RESET_N
and
PERST#
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
RESET_N or PERST# pin. Higher protection level
can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to
accessible point.
Connecting the
RESET_N or PERST# input to an external device (e.g. application processor), an open drain
output can be directly connected without any external pull-up, as described in Figure 25 and Table 16. The
internal pull-up resistor provided by the module pulls the line to the high logic level when the
RESET_N or
PERST# pin is not forced low by the application processor. A compatible push-pull output of an application
processor can be used too.
TOBY-L1 series
V_BCKP
23
RESET_N
Power-on
push button
ESD
Open
Drain
Output
Application
Processor
TOBY-L1 series
V_BCKP
23
RESET_N
TP TP
10 k Ω 10 k
Ω
MPCI-L1 series
22
PERST#
Power-on
push button
ESD
Open
Drain
Output
Application
Processor
MPCI-L1 series
22
PERST#
10 k
Ω
10 k
Ω
2.5V
2.5V
Figure 25: RESET_N and PERST# application circuits using a push button and an open drain output of an application processor
Reference Description Remarks
ESD Varistor for ESD protection CT0402S14AHSG – EPCOS
Table 16: Example of ESD protection component for the RESET_N application circuit