Installation Instructions

LISA-U2 series - System Integration Manual
UBX-13001118 - R19 Early Production Information System description
Page 19 of 175
The module cannot be switched on if the VCC voltage value is below the specified normal operating
range minimum limit. Ensure that the input voltage at VCC pins is above the minimum limit of the normal
operating range for more than 3 s after the start of the module switch-on sequence.
When LISA-U2 series modules are in operation, the voltage provided to VCC pins can go outside the normal
operating range limits but must be within the extended operating range limits specified in LISA-U2 series Data
Sheet [1]. Occasional deviations from the ETSI specifications may occur when the input voltage at VCC pins is
outside the normal operating range and is within the extended operating range.
LISA-U2 series modules switch off when VCC voltage value drops below the specified extended operating
range minimum limit: ensure that the input voltage at VCC pins never drops below the minimum limit of
the extended operating range when the module is switched on, not even during a GSM transmit burst,
where the current consumption can rise up to maximum peaks of 2.5 A in case of a mismatched antenna
load.
Operation above the normal operating range maximum limit is not recommended and extended
exposure beyond it may affect device reliability.
Stress beyond the VCC absolute maximum ratings can cause permanent damage to the module:
if necessary, voltage spikes beyond VCC absolute maximum ratings must be restricted to values
within the specified limits by using appropriate protection.
When designing the power supply for the application, pay specific attention to power losses and
transients. The DC power supply must be able to provide a voltage profile to the VCC pins with the
following characteristics:
o Voltage drop during transmit slots must be lower than 400 mV
o No undershoot or overshoot at the start and at the end of transmit slots
o Voltage ripple during transmit slots must be minimized:
lower than 70 mVpp if f
ripple
≤ 200 kHz
lower than 10 mVpp if 200 kHz < f
ripple
≤ 400 kHz
lower than 2 mVpp if f
ripple
> 400 kHz
Time
undershoot
overshoot
ripple
ripple
drop
Voltage
3.8 V
(typ)
RX
slot
unused
slot
unused
slot
TX
slot
unused
slot
unused
slot
MON
slot
unused
slot
RX
slot
unused
slot
unused
slot
TX
slot
unused
slot
unused
slot
MON
slot
unused
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
GSM frame
4.615 ms
(1 frame = 8 slots)
Figure 4: Description of the VCC voltage profile versus time during a GSM call