Ublox TOBY-L2 series, Руководство по системной интеграции

Страница: 117 / 164

TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R28 Design-in Page 117 of 164
2.9 Mini PCIe specific signals (W_DISABLE#, LED_WWAN#)
☞
Mini PCI Express specific signals (W_DISABLE#, LED_WWAN#) are not available on TOBY-L2
series.
2.9.1.1 Guidelines for W_DISABLE# circuit design
As described in Figure 66 , the MPCI-L2 series modules W_DISABLE# wireless disable input is
equipped with an internal pull-up to the 3.3Vaux supply: an external pull-up resistor is not required
and should not be provided.
If connecting the W_DISABLE# 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 should be provided close to accessible point, as described in
Figure 66 and Table 41 .
☞
ESD sensitivity rating of the W_DISABLE# 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
an accessible push button is directly connected to the W_DISABLE# pin, and it can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor) close to accessible point.
An open drain output is suitable to drive the W_DISABLE# input from an application processor as it is
equipped with an internal pull-up to the 3.3Vaux supply as described in
Figure 66 .
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 disabling of the radio
operations.
MPCI-L2 series
3.3Vaux
20
W_DISABLE#
Power-on
push button
ESD
Open
Drain
Output
Application
Processor
MPCI-L2 series
3.3Vaux
20 W_DISABLE#
TP TP
22 k 
22 k 
Figure 66: W_DISABLE# application circuit using a push button and an open drain output of an application processor
Reference Description Part Number – Manufacturer
ESD Varistor for ESD protection CT0402S14AHSG – EPCOS
Table 41: Example of ESD protection component for the W_DISABLE# application circuit
☞
If the W_DISABLE# functionality is not required by the application, the pin can be left
unconnected.