Installation Instructions

LISA-U2 series - System Integration Manual
UBX-13001118 - R19 Early Production Information System description
Page 82 of 175
If a 1.8 V Application Processor is used, the SPI Master pins can be directly connected to the specific LISA-U2 SPI
slave pins as described in Figure 45. It is recommended to tri-state the output pins of the SPI Master (i.e. set in
high impedance mode) when LISA-U2 module is in power-down mode, when the external reset is forced low
and during the module power-on sequence (at least for 3 s after the start-up event), to avoid latch-up of circuits
and allow a proper boot of the module.
MOSI
Application processor
(1.8V SPI master)
MISO
SCLK
Interrupt
GND
LISA-U2 series
(1.8V SPI slave)
56
SPI_MOSI
59
SPI_MRDY
57
SPI_MISO
55
SPI_SCLK
58
SPI_SRDY
GND
GPIO
Figure 45: IPC / SPI Interface application circuit connecting LISA-U2 series 1.8V SPI slave to a 1.8V SPI master
If a 3.0 V SPI Master Application Processor is used, implement a circuit with appropriate unidirectional voltage
translators with tri-state (i.e. high impedance) mode controlled by the application processor, as described in
Figure 46.
4
V_INT
MOSI
Application processor
(3.0V SPI master)
MISO
SCLK
Interrupt
GND
LISA-U2 series
(1.8V SPI slave)
56
SPI_MOSI
57
SPI_MISO
55
SPI_SCLK
58
SPI_SRDY
GND
U1
VCC
GPIO
GPIO
59
SPI_MRDY
1V8
B1 A1
GND
U1
B3A3
VCCBVCCA
Unidirectional
Voltage Translator
C1
C2
3V0
DIR3
DIR2
OE
DIR1
B2 A2
B4A4
DIR4
1V8
B1 A1
GND
U2
VCCBVCCA
Unidirectional
Voltage Translator
C3
C4
3V0
DIR2
DIR1
OE
B2 A2
Figure 46: IPC / SPI Interface application circuit connecting LISA-U2 series 1.8V SPI slave to a 3.0V SPI master
Reference
Description
Part Number - Manufacturer
C1, C2, C3, C4
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
U1
Unidirectional Voltage Translator
SN74AVC4T774 - Texas Instruments
U2
Unidirectional Voltage Translator
SN74AVC2T245 - Texas Instruments
Table 36: Components for IPC / SPI Interface application circuit connecting LISA-U2 series 1.8V SPI slave to a 3.0V SPI master