User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information Design-In
Page 92 of 116
 Power On (PWR_ON): is the digital input to switch-on the LISA-U1/LISA-H1 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/LISA-H1 series modules and the host processor, with a data rate up to 20 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/LISA-H1 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