u-blox SARA-R4 Series System Integration Manual

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SARA-R4 series - System Integration ManualUBX-16029218 - R06 System descriptionPage 20 of 1021.6.2 Module power-offSARA-R4 series can be properly switched off by: AT+CPWROFF command (see SARA-R4 series AT Commands Manual [2]). The current parameter settings aresaved in the module’s non-volatile memory and a proper network detach is performed. Low pulse on the PWR_ON pin for a valid time period (see SARA-R4 series Data Sheet [1]).An abrupt under-voltage shutdown occurs on SARA-R4 series modules when the VCC module supply isremoved. If this occurs, it is not possible to perform the storing of the current parameter settings in the module’snon-volatile memory or to perform the proper network detach.It is highly recommended to avoid an abrupt removal of the VCC supply during SARA-R4 series modulesnormal operations.An abrupt hardware shutdown occurs on SARA-R4 series modules when a low level is applied on RESET_N pin.In this case, the current parameter settings are not saved in the module’s non-volatile memory and a propernetwork detach is not performed.It is highly recommended to avoid an abrupt hardware shutdown of the module by forcing a low level onthe RESET_N input pin during module normal operation: the RESET_N line should be set low only if resetor shutdown via AT commands fails or if the module does not reply to a specific AT command after a timeperiod longer than the one defined in the SARA-R4 series AT Commands Manual [2].Figure 6 describes the SARA-R4 series modules switch-off sequence started by means of the AT+CPWROFFcommand, allowing storage of current parameter settings in the module’s non-volatile memory and a propernetwork detach, with the following phases: When the +CPWROFF AT command is sent, the module starts the switch-off routine. The module replies OK on the AT interface: the switch-off routine is in progress. At the end of the switch-off routine, all the digital pins are tri-stated and all the internal voltage regulatorsare turned off, including the generic digital interfaces supply (V_INT). Then, the module remains in switch-off mode as long as a switch on event does not occur (e.g. applying aproper low level to PWR_ON), and enters not-powered mode if the supply is removed from the VCC pins.VCCPWR_ONRESET_NV_INTInternal ResetSystem StateBB Pads State OperationalOFFTristate / FloatingONOperational → TristateAT+CPWROFFsent to the moduleOKreplied by the moduleVCC can beremovedFigure 6: SARA-R4 series switch-off sequence by means of AT+CPWROFF commandThe Internal Reset signal is not available on a module pin, but it is recommended to monitor the V_INTpin to sense the end of the switch-off sequence: VCC supply can be removed only after V_INT goes low.The duration of each phase in the SARA-R4 series modules’ switch-off routines can largely vary dependingon the application / network settings and the concurrent module activities.