Integration Manual

LISA-U2 series - System Integration Manual
UBX-13001118 - R25 System description Page 106 of 182
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 the 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).
1:1 scaling
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 a 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.