TOBY-L4 series - System Integration Manual
UBX-16024839 - R04
Design-in
Page 70 of 143
2.3.3
Module / host configuration selection
Host Select pins are not supported by the "50" product version.
2.3.3.1
Guidelines for HOST_SELECTx circuit design
TOBY-L4 series modules include two 1.8 V digital pins (
HOST_SELECT0
,
HOST_SELECT1
), which can be
configured for External Interrupt detection or as GPIO by means of the uCPU API: the pins can be connected to
external devices following the guidelines provided in section 2.10.
Do not apply voltage to the
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 correct boot of the module.
The ESD sensitivity rating of the
HOST_SELECT0
and
HOST_SELECT1
pins is 1 kV (HBM as per JESD22-
A114). A 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 the
accessible points.
If the functionality of the
HOST_SELECT0
and
HOST_SELECT1
pins is not required, the pins can be left
unconnected on the application board.
2.3.3.2
Guidelines for HOST_SELECTx layout design
The design for the
HOST_SELECT0
and
HOST_SELECT1
pins functions is generally not critical for layout.