Installation Instructions
LISA-U2 series - System Integration Manual
UBX-13001118 - R19 Early Production Information Appendix
Page 162 of 175
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.
Clean and stable supply is required by LISA-U2 as by LISA-U1 series: low ripple and low voltage drop must be
guaranteed at VCC pins. The voltage provided has to be within the normal operating range limits to allow
module switch-on and has to 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.
PWR_ON low pulse time required to switch-on the module is different in comparison to LISA-U1 series modules.
LISA-U2 series can be switched off forcing PWR_ON pin to the low level for at least 1 s.
PWR_ON and RESET_N input voltage thresholds are slightly changed in comparison to LISA-U1 series modules,
but this is not relevant driving PWR_ON and RESET_N inputs by open drain / collector drivers as recommended.
V_BCKP operating characteristics are slightly changed in comparison to LISA-U1 series modules.
The voltage level of all the digital interfaces of LISA-U2 series modules is 1.8 V as for LISA-U1 series modules.
The internal active pull-up / pull-down values at digital interface input pins and the current capability of digital
interface output pins LISA-U2 series modules are slightly changed in comparison to LISA-U1 series modules.
UART of LISA-U2 series supports autobauding (default setting) and 921600 b/s baud rate.
LISA-U2 series provide one additional USB CDC for remote SIM Access Profile (SAP).