LISA-U2 series - System integration manual
UBX-13001118 - R27
System description
Page 105 of 183
C1-Public
☞
The GPIO pins’ ESD sensitivity rating is 1 kV (Human Body Model according to JESD22
-A114F).
Higher protection levels could be required if the lines are externally accessible on the application
board. Higher protection levels can be achieved by mounting an ESD protection (e.g. EPCOS
CA05P4S14THSG varistor array) on the lines connected to these pins, close to accessible points.
An application circuit for a typical GPIOs usage is described in
•
Network indication function provided by the
GPIO1
pin
•
GNSS supply enable function provided by the
GPIO2
pin
•
GNSS data ready function provided by the
GPIO3
pin
•
GNSS RTC sharing function provided by the
GPIO4
pin
•
SIM card detection function provided by the
GPIO5
pin
☞
Use transistors with at least an integrated resistor in the base pin or otherwise put a 10 k
Ω
resistor
on the board in series with the GPIO.
☞
If the GPIO pins are not used, they can be left unconnected on the application board.
☞
Any external signal connected to GPIOs must be tri-stated when the module is in power-down
mode, when the external reset is forced low, and during the module power-on sequence (at least
for 3 seconds after the start-up event), to avoid latch-up of circuits and allow a proper boot of the
module. If the external signals connected to the module cannot be tri-stated, insert a multi-
channel digital switch (e.g. Texas Instruments SN74CB3Q16244, TS5A3159, or TS5A63157)
between the two-circuit connections and set to high impedance during module power-down mode,
when the external reset is forced low, and during the power-on sequence.
SIM card holder
SW1
SW2
4
V_INT
51
GPIO5
R4
R3
OUT
IN
GND
LDO Regulator
SHDN
3V8
1V8
GPIO3
GPIO4
TxD1
EXTINT0
23
24
R1
VCC
GPIO2
21
LISA-U2 series
u-blox GNSS
1.8 V receiver
U1
J1
C1
R5
R7
3V8
Network Indicator
R6
GPS Supply Enable
GPS Data Ready
GPS RTC Sharing
SIM Detection
20
GPIO1
DL1
T1
D1
R2
Figure 52: GPIO application circuit
Reference
Description
Part Number - Manufacturer
R1
47 k
Ω
Resistor 0402 5% 0.1 W
Various manufacturers
U1
Voltage Regulator for GNSS receiver
See GNSS Module Hardware Integration Manual
R2
4.7 k
Ω
Resistor 0402 5% 0.1 W
Various manufacturers
R3
1 k
Ω
Resistor 0402 5% 0.1 W
Various manufacturers
R4
470 k
Ω
Resistor 0402 5% 0.1 W
Various manufacturers
D1
ESD Transient Voltage Suppressor
USB0002RP or USB0002DP - AVX
