LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
Design-In
Page 98 of 125
Power On (PWR_ON):
is the digital input to switch-on the LISA-U1 series modules. Ensure that the voltage
level is well defined during operation and no transient noise is coupled on this line, otherwise the module
might detect a spurious power on request
2.2.1.7
High-speed digital pins
The Serial Peripheral Interface Bus (SPI) interface can be used for high speed data transfer (UMTS/HSPA) between
the LISA-U1 series modules and the host processor, with a data rate up to 26 Mb/s (see Section 1.9.3). The
high-speed data rate is carried by signals
SPI_SCLK
,
SPI_MISO
and
SPI_MOSI
, while
SPI_SRDY
and
SPI_MRDY
behave as handshake signals with relatively low activity.
High-speed signals become sources of digital noise, route away from RF and other sensitive analog signals
Keep routing short and minimize parasitic capacitance to preserve digital signal integrity
2.2.1.8
Digital pins and supplies
External Reset (RESET_N):
input for external reset, a logic low voltage will reset the module
SIM Card Interface (VSIM, SIM_CLK, SIM_IO, SIM_RST)
: the SIM layout may be critical if the SIM card is
placed far away from the LISA-U1 series modules or in close proximity to the RF antenna. In the first case the
long connection can cause the radiation of some harmonics of the digital data frequency. In the second case
the same harmonics can be picked up and create self-interference that can reduce the sensitivity of GSM
Receiver channels whose carrier frequency is coincidental with harmonic frequencies. The latter case, placing
the RF bypass capacitors, suggested in Figure 20, near the SIM connector will mitigate the problem. In
addition, since the SIM card is typically accessed by the end user, it can be subjected to ESD discharges: add
adequate ESD protection to protect module SIM pins near the SIM connector.
Digital Audio (I2S_CLK, I2S_RX, I2S_TX, I2S_WA)
: the I
2
S interface requires the same consideration
regarding electro-magnetic interference as the SIM card. Keep the traces short and avoid coupling with RF
line or sensitive analog inputs
DDC (SCL, SDA)
: the DDC interface requires the same consideration regarding electro-magnetic
interference as the SIM card. Keep the traces short and avoid coupling with RF line or sensitive analog inputs
UART (TXD, RXD, CTS, RTS, DSR, RI, DCD, DTR)
: the serial interface requires the same consideration
regarding electro-magnetic interference as the SIM card. Keep the traces short and avoid coupling with RF
line or sensitive analog inputs
General Purpose I/O (GPIOx)
: the general purpose input/output pins are generally not critical for layout
Reserved pins
: these pins are reserved for future use. Leave them unconnected on the baseboard
USB detection
(
VUSB_DET
): this input will generate an interrupt to the baseband processor for USB
detection. The USB supply (5.0 V typ.) must be provided to
VUSB_DET
by the connected USB host to enable
the USB interface of the module
Interfaces Supply
(
V_INT
): this supply output is generated by an integrated switching step down converter,
used internally to supply the digital interfaces. Because of this, it can be a source of noise: avoid coupling
with sensitive signals
