Installation Instructions

LISA-U2 series - System Integration Manual
UBX-13001118 - R19 Early Production Information System description
Page 103 of 175
The recommended application circuit for the module status indication function, provided by LISA-U2 series
module GPIO1 and GPIO13 pins to indicate module status (power-off mode, i.e. module switched off, versus
idle, active or connected mode, i.e. module switched on), is described in Figure 53.
The logic level of the pin configured to provide module status indication, that is set high when the module is
switched on (with interfaces configured) and low when the module is switched off, is inverted by a transistor
biased by the V_BCKP supply, which is generated by the module when a valid VCC is applied.
A pull-down resistor is provided at the GPIO1 output (which provides module status indication) to fix a low level
at inverting transistor input when GPIO1 is floating, i.e. when the module is switched off, so that high logic level
is present at the application processor input when the module is switched off and low logic level when the
module is switched on (i.e. the opposite logic level of the GPIO).
Input (1.8V)
V_BCKP
2
LISA-U2 series
Application
processor
R1
R3
Module Status Indication
R2
20
GPIO1
T1
Figure 53: Module status indication application circuit
Reference
Description
Part Number - Manufacturer
R1, R3
47 kΩ Resistor 0402 5% 0.1 W
Various manufacturers
R2
100 kΩ Resistor 0402 5% 0.1 W
Various manufacturers
T1
NPN BJT Transistor
BC847 - Infineon
Table 44: Components for module status indication application circuit
1.13 Reserved pins (RSVD)
LISA-U2 modules have pins reserved for future use. All the RSVD pins, except pin number 5, can be left
unconnected on the application board.
Pin 5 (RSVD) must be connected to GND.