u-blox LARA-R2 series System Integration Manual page 77

2.2.1.10 Guidelines for removing VCC supply
As described in section 1.6.2 and Figure 14, the VCC supply can be removed after the end of LARA-R2 series
modules internal power-off sequence, which has to be properly started sending the AT+CPWROFF command
(see u-blox AT Commands Manual [2]).
Removing the VCC power can be useful in order to minimize the current consumption when the LARA-R2 series
modules are switched off. Then, the modules can be switched on again by re-applying the VCC supply.
If the VCC supply is generated by a switching or an LDO regulator, the application processor may control the
input pin of the regulator which is provided to enable / disable the output of the regulator (as for example the
RUN input pin for the regulator described in Figure 26, the INH input pin for the regulator described in Figure 27,
the SHDNn input pin for the regulator described in Figure 28, the EN input pin for the regulator described in
Figure 29), in order to apply / remove the VCC supply.
If the regulator that generates the VCC supply does not provide an on / off pin, or for other applications such as
the battery-powered ones, the VCC supply can be switched off using an appropriate external p-channel MOSFET
controlled by the application processor by means of a proper inverting transistor as shown in Figure 35, given
that the external p-channel MOSFET has provide:

Very low R (for example, less than 50 m), to minimize voltage drops
DS(ON)

Adequate maximum Drain current (see LARA-R2 series Data Sheet [1] for module consumption figures)

Low leakage current, to minimize the current consumption
VCC Supply Source
Application
GPIO
Processor
GND
Figure 35: Example of application circuit for VCC supply removal
Reference Description
R1
47 k Resistor 0402 5% 0.1 W
R2 10 k Resistor 0402 5% 0.1 W
R3
100 k Resistor 0402 5% 0.1 W
T1 P-Channel MOSFET Low On-Resistance
T2 NPN BJT Transistor
C1
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
C2 10 nF Capacitor Ceramic X7R 0402 10% 16 V
C3 100 nF Capacitor Ceramic X7R 0402 10% 16 V
C4 56 pF Capacitor Ceramic C0G 0402 5% 25 V
C5 15 pF Capacitor Ceramic C0G 0402 5% 25 V
C6 8.2 pF Capacitor Ceramic C0G 0402 5% 50 V
Table 27: Components for VCC supply removal application circuit
It is highly recommended to avoid an abrupt removal of the VCC supply during LARA-R2 series modules
normal operations: the power off procedure must be started by the AT+CPWROFF command, waiting the
command response for a proper time period (see u-blox AT Commands Manual [2]), and then a proper
VCC supply has to be held at least until the end of the modules' internal power off sequence, which
occurs when the generic digital interfaces supply output (V_INT) is switched off by the module.
UBX-16010573 - R02
T1
R3
+
R2
C1
T2
R1
Objective Specification
LARA-R2 series - System Integration Manual
LARA-R2 series
51
52
53
C2 C3 C4 C5 C6
Part Number - Manufacturer
RC0402JR-0747KL - Yageo Phycomp
RC0402JR-0710KL - Yageo Phycomp
RC0402JR-07100KL - Yageo Phycomp
AO3415 - Alpha & Omega Semiconductor Inc.
BC847 - Infineon
T520D337M006ATE045 - KEMET
GRM155R71C103KA01 - Murata
GRM155R61A104KA01 - Murata
GRM1555C1E560JA01 - Murata
GRM1555C1E150JA01 - Murata
GRM1555C1H8R2DZ01 - Murata
VCC
VCC
VCC
GND
Page 77 of 148
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