Integration Manual
SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R13 Design-in Page 52 of 119
2.2.1.9 Guidelines for removing VCC supply
Removing the VCC power can be useful to minimize the current consumption when the SARA-R4/N4 series modules are
switched off or when the modules are in deep sleep Power Saving Mode.
In applications in which the module is paired to a host application processor equipped with a RTC, the module can execute
standard PSM procedures, store NAS protocol context in non-volatile memory, and rely on the host application processor
to run its RTC and to trigger wake-up upon need. The application processor can disconnect the VCC supply source from
the module and zero out the module’s PSM current.
The VCC supply source can be removed using an appropriate low-leakage load switch or p-channel MOSFET controlled by
the application processor as shown in Figure 26, given that the external switch has provide:
• Very low leakage current (for example, less than 1 µA), to minimize the current consumption
• Very low R
DS(ON)
series resistance (for example, less than 50 mΩ), to minimize voltage drops
• Adequate maximum Drain current (see the SARA-R4/N4 series Data Sheet [1] for module current consumption
figures)
C3
GND
C2C1 C4
SARA-R4/ N4
52
VCC
53
VCC
51
VCC
VCC Supply Source
GND
C5
U1
VOUTVIN
VBIAS
ON
CT
GND
4
V_INT
15
PWR_ON
R1
R2
T1
GPIO
Applicat ion
Processor
GPIO
GPIO
+
Figure 26: Example of application circuit for VCC supply removal
Reference Description Part Number - Manufacturer
C1
100 µF Capacitor Tantalum B_SIZE 20% 6.3V 15mΩ
T520B107M006ATE015 – Kemet
C2 10 nF Capacitor Ceramic X7R 0402 10% 16 V GRM155R71C103KA01 - Murata
C3 100 nF Capacitor Ceramic X7R 0402 10% 16 V GRM155R61A104KA01 - Murata
C4 68 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1H680JA01 - Murata
C5 15 pF Capacitor Ceramic C0G 0402 5% 25 V GRM1555C1E150JA01 - Murata
R1, R3
47 kΩ Resistor 0402 5% 0.1 W
RC0402JR-0747KL - Yageo Phycomp
R2
10 kΩ Resistor 0402 5% 0.1 W
RC0402JR-0710KL - Yageo Phycomp
T1 NPN BJT Transistor BC847 - Infineon
U1 Ultra-Low Resistance Load Switch TPS22967 - Texas Instruments
Table 18: Components for VCC supply removal application circuit
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It is highly recommended to avoid an abrupt removal of the VCC supply during SARA-R4/N4 series normal operations:
the VCC supply can be removed only after V_INT goes low, indicating that the module has entered Deep-Sleep Power
Saving Mode or Power-Off Mode.
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See the section 2.2.1.10, and in particular Figure 27 / Table 19, for the parts recommended to be provided if the
application device integrates an internal antenna.