LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 19 of 125
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:
Voltage drop during transmit slots must be lower than 400 mV
No undershoot or overshoot at the start and at the end of transmit slots
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 5: Description of the VCC voltage profile versus time during a GSM call
Any degradation in power supply performance (due to losses, noise or transients) will directly affect the
RF performance of the module since the single external DC power source indirectly supplies all the
digital and analog interfaces, and also directly supplies the RF power amplifier (PA).
The voltage at the
VCC
pins must ramp from 2.5 V to 3.2 V within 1 ms. This
VCC
slope allows a proper
switch on of the module, that is switched on when the voltage rises to the
VCC
operating range starting
from a voltage value lower than 2.25 V.
1.5.2.1
VCC application circuits
LISA-U1 series modules must be supplied through the
VCC
pins by one (and only one) proper DC power supply
that must be one of the following:
Switching regulator
Low Drop-Out (LDO) linear regulator
Rechargeable Li-Ion battery
Primary (disposable) battery
