User Manual

TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R08 Early Production Information Design-in
Page 87 of 158
2.3.2.2 Guidelines for RESET_N and PERST# layout design
The RESET_N and PERST# circuits require careful layout due to the pin function: 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 reset request. It is recommended to keep the connection line to RESET_N and PERST# pins as short
as possible.
2.3.3 Module configuration selection by host processor
The HOST_SELECT0 and HOST_SELECT1 pins are not available on MPCI-L2 series modules.
2.3.3.1 Guidelines for HOST_SELECTx circuit design
The functionality of the HOST_SELECT0 and HOST_SELECT1 pins is not supported by the TOBY-L2 “00”,
“01”, and “50” product versions: the two input pins should not be driven by the host application
processor or any other external device.
TOBY-L2 series modules include two input pins (HOST_SELECT0 and HOST_SELECT1) for the selection of the
module configuration by the host application processor.
Guidelines for HOST_SELECT0 and HOST_SELECT1 pins circuit design will be described in detail in a
successive release of the document.
Do not apply voltage to HOST_SELECT0 and HOST_SELECT1 pins before the switch-on of their supply
source (V_INT), to avoid latch-up of circuits and allow a proper boot of the module. If the external signals
connected to the cellular module cannot be tri-stated or set low, insert a multi channel digital switch (e.g.
TI SN74CB3Q16244, TS5A3159, or TS5A63157) between the two-circuit connections and set to high
impedance before V_INT switch-on.
ESD sensitivity rating of the HOST_SELECT0 and HOST_SELECT1 pins is 1 kV (HBM as per JESD22-A114).
Higher protection level could be required if the lines are externally accessible and it can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible points
If the HOST_SELECT0 and HOST_SELECT1 pins are not used, they can be left unconnected on the
application board.
2.3.3.2 Guidelines for HOST_SELECTx layout design
The input pins for the selection of the module configuration by the host application processor (HOST_SELECT0
and HOST_SELECT1) are generally not critical for layout.