Integration Manual

LISA-U2 series - System Integration Manual
UBX-13001118 - R25 System description Page 18 of 182
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 1.5.4).
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 1.5.3). It is
important that the system power supply circuit is able to support peak power (see the LISA-U2 series
Data Sheet [1] 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
the LISA-U2 series Data Sheet [1]. Complete functionality of the module is only guaranteed within the
specified minimum and maximum VCC voltage normal operating range.
☞ 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 seconds after the start of the module switch-on sequence.
When LISA-U2 series modules are in operation, the voltage provided to VCC pins can exceed the
normal operating range limits but must be within the extended operating range limits specified in the
LISA-U2 series Data Sheet [1]. Occasional deviations from the ETSI specifications may occur when the
input voltage at the VCC pins is outside the normal operating range and is within the extended
operating range.