LISA-U2 series - System integration manual
UBX-13001118 - R27
System description
Page 18 of 183
C1-Public
The pins with supply functions are listed in
and
LISA-U2 series modules must be supplied via the
VCC
pins. There is only one main power supply input,
available on the three
VCC
pins that must be all connected to the external power supply.
The
VCC
pins are directly connected to the RF power amplifiers and to the integrated Power
Management Unit (PMU) within the module: all supply voltages needed by the module are generated
from the
VCC
supply by integrated voltage regulators.
V_BCKP
is the Real Time Clock (RTC) supply. When the
VCC
voltage is within the valid operating
range, the internal PMU supplies the Real Time Clock and the same supply voltage will be available to
the
V_BCKP
pin. If the
VCC
voltage is under the minimum operating limit (for example, during not
powered mode), the Real Time Clock can be externally supplied via the
V_BCKP
pin (see section
When a 1.8 V or a 3 V SIM card type is connected, LISA-U2 series modules automatically supply the
SIM card via the
VSIM
pin. Activation and deactivation of the SIM interface with automatic voltage
switch from 1.8 to 3 V is implemented, in accordance with the ISO-IEC 7816-3 specifications.
The same voltage domain used internally to supply the digital interfaces is also available on the
V_INT
pin, to allow more economical and efficient integration of the LISA-U2 series modules in the final
application.
The integrated Power Management Unit also provides the control state machine for system start-up
and system reset control.
1.5.2
Module supply (VCC)
The LISA-U2 series modules must be supplied through the
VCC
pins by a DC power supply. Voltages
must be stable: during operation, the current drawn from
VCC
can vary by some orders of magnitude,
especially due to surging consumption profile of the GSM system (described in the section
). It is
important that the system power supply circuit is able to support peak power (see the LISA-U2 series
data sheet
for the detailed specifications).
Name
Description
Remarks
VCC
Module power supply input
VCC
pins are internally connected, but all the available
pads must be connected to the external supply in order
to minimize the power loss due to series resistance.
Clean and stable supply is required: low ripple and low
voltage drop must be guaranteed.
Voltage provided must always be above the minimum
limit of the operating range.
Consider that during a GSM call there are large current
spikes in connected mode.
GND
Ground
GND
pins are internally connected but a good (low
impedance) external ground can improve RF
performance: all available pads must be connected to
ground.
Table 6: Module supply pins
☞
VCC
pins ESD sensitivity rating is 1 kV (Human Body Model according to JESD22-A114F). Higher
protection levels can be required if the line is externally accessible on the application board. Higher
protection level can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG
varistor array) on the line connected to this pin, close to accessible points.
The voltage provided to the
VCC
pins must be within the normal operating range limits as specified in
. Complete functionality of the module is only guaranteed within the
specified minimum and maximum
VCC
voltage normal operating range.
