Integration Manual

TSD-19090601 - R15 Contents Page 104 of 143
T1
P-Channel MOSFET Low On-Resistance
IRLML6401 - International Rectifier or NTZS3151P - ON
Semi
T2
NPN BJT Transistor
BC847 - Infineon
C1
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C104KA01 - Murata
Table 40: Components for connecting TOBY-L3 series modules to u-blox 1.8 V GNSS devices using V_INT as supply
Connection with u-blox 3.0 V GNSS devices
Figure 39 shows an application circuit for connecting the cellular modules to a u-blox 3.0 V GNSS device:
 As the SDA and SCL pins of the cellular module are not tolerant up to 3.0 V, the connection to the
related I
2
C pins of the u-blox 3.0 V GNSS device must be provided using a suitable I
2
C-bus Bidirectional
Voltage Translator with appropriate pull-up resistors (e.g. the TI TCA9406 additionally provides the partial
power down feature so that the GNSS 3.0 V supply can be ramped up before the V_INT 1.8 V cellular
supply).
 GPIO2 pin is connected to the shutdown input pin (SHDNn) of the LDO regulators providing the 3.0 V
supply rail for the u-blox 3.0 V GNSS device implementing the “GNSS enable” function, with an
appropriate pull-down resistor mounted on the GPIO2 line to avoid an improper switch-on of the u-
blox GNSS device.
 As the GPIO3 pin of the cellular module is not tolerant up to 3.0 V, the connection to the related pin of
the u-blox 3.0 V GNSS device must be provided using a suitable Unidirectional General Purpose Voltage
Translator (e.g. TI SN74LVC1T45, which additionally provides the partial power down feature so that the
3.0 V GNSS supply can be also ramped up before the V_INT 1.8 V rail).
 The V_BCKP backup supply input pin of the GNSS device is connected to the external battery as in the
application circuit for a u-blox 1.8 V GNSS device.