User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information System description
Page 17 of 116
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-U1/LISA-H1 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 to 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-U1/LISA-H1 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-U1/LISA-H1 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 (refer to LISA-U1/LISA-H1 series Data Sheet [1] for
specification).
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 3: Module supply pins
VCC pins ESD rating is 1 kV (contact discharge). A higher protection level can be required if the line is
externally accessible on the application board. A higher protection level can be achieved by mounting an
ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) on the line connected to this pin.
The voltage provided to the VCC pins must be within the normal operating range limits as specified in the
LISA-U1/LISA-H1 series Data Sheet [1]. Complete functionality of the module is only guaranteed within the
specified minimum and maximum VCC voltage operating range.
Ensure that the input voltage at the VCC pins never drops below the minimum limit of the operating
range when the module is switched on. This is the case even during a GSM transmit burst, where the
current consumption can rise up to minimum peaks of 2.5 A in case of a mismatched antenna load.
Operation above the operating range maximum limit is not recommended and extended
exposure beyond it may affect device reliability.