LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 18 of 125
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 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 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 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 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 4: Module supply pins
VCC
pins ESD sensitivity rating is 1 kV (Human Body Model according to JESD22-A114F). Higher
protection level 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.
The voltage provided to the
VCC
pins must be within the normal operating range limits as specified in the
[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.
