Integration Manual

LISA-U2 series - System Integration Manual
UBX-13001118 - R25 Appendix Page 167 of 182
A.2 Software migration
A.2.1 Software migration from LISA-U1 series to LISA-U2 series modules
Software migration from LISA-U1 to LISA-U2 series cellular modules is a straight-forward procedure.
Nevertheless, there are some differences to be considered with firmware versions. Like its
predecessors, the LISA-U2 series cellular module supports AT commands according to 3GPP
standards: TS 27.007 [4], TS 27.005 [5], TS 27.010 [6] and the u-blox AT command extension.
Backward compatibility has been maintained as far as possible.
☞ For the complete list of supported AT commands and their syntax, see the u-blox AT Commands
Manual [2].
A.3 Hardware migration
A.3.1 Hardware migration from LISA-U1 series to LISA-U2 series modules
LISA-U2 series modules have been designed with backward compatibility in mind, but some minor
differences were unavoidable. These minor differences will however not be relevant for the majority of
the LISA-U1 series designs.
A clean and stable supply is required by LISA-U2 as for the LISA-U1 series: low ripple and low voltage
drop must be guaranteed at the VCC pins. The voltage provided must be within the normal operating
range limits to allow module switch-on and must be above the minimum limit of the extended
operating range to avoid module switch-off. Consider that there are large current spikes in connected
mode when a GSM call is enabled.
LISA-U2 series provide wider VCC input voltage range compared to LISA-U1 series.
The ANT pin has 50 Ω nominal characteristic impedance and must be connected to the antenna
through a 50 Ω transmission line to allow transmission and reception of radio frequency (RF) signals
in the 2G and 3G operating bands. The recommendations of the antenna producer for correct
installation and deployment (PCB layout and matching circuitry) must be followed.
The antenna and the whole RF circuit must provide optimal radiating characteristics on the entire
supported bands: note that LISA-U2 supports different 3G bands in comparison to LISA-U1 series
modules.
An external application circuit can be implemented on the application device integrating LISA-U2
series modules to satisfy ESD immunity test requirements at the antenna interface, as described in
Figure 68 and Table 53 in section 2.5.3. The same application circuit is not applicable for LISA-U1
series.
LISA-U230 modules provide the RF antenna input for Rx diversity on the pin 74 (named ANT_DIV): it
has an impedance of 50 Ω. The same pad is a reserved pin on LISA-U1 series and on the other LISA-U2
series modules.
Analog audio interfaces are not supported by LISA-U2 series modules, but a second 4-wire I
2
S digital
audio interface is provided instead of the 4 analog audio pins. The same 4 pins can be configured as
GPIO on LISA-U2 series modules.
Analog audio can be provided with an external audio codec connected to LISA-U2 series modules,
implementing the application circuit described in Figure 50. An external audio codec can be connected
to the I
2
S digital audio interface of LISA-U1 series modules as shown in the same application circuit
described in Figure 50. In this case, the application processor should properly control the audio codec
by I
2
C interface and should properly provide clock reference to the audio codec. This circuit allows
migration from LISA-U1 series to LISA-U2 series, providing analog audio with the same application
circuit.