LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
System description
Page 36 of 125
1.6.2
Module power off
The correct way to switch off LEON-G100 / LEON-G200 modules is by means of the AT command AT+CPWROFF
(more details in
u-blox AT Commands Manual
[2]): in this way the current parameter settings are saved in the
module’s non-volatile memory and a proper network detach is performed.
An under-voltage shutdown will be done if
VCC
falls below the extended operating range minimum limit (see
LEON-G100 / LEON-G200
Data Sheet
[1]), but in this case the current parameter settings are not saved in the
module’s non-volatile memory and a proper network detach cannot be performed.
When the AT+CPWROFF command is sent, the module starts the switch-off routine replying OK on the AT
interface: during this phase, the current parameter settings are saved in the module’s non-volatile memory, a
network detach is performed and all module interfaces are disabled (i.e. the digital pins are locked in tri-state by
the module). Since the time to perform a network detach depends on the network settings, the duration of this
phase can differ from the typical value reported in Figure 20. At the end of the switch-off routine, the module
pulls the
RESET_N
pin low to indicate that it is in power-off mode: all the digital pins are locked in tri-state by
the module and all the internal LDO voltage regulators except the RTC supply (
V_BCKP
) are turned off in a
defined power-off sequence. The module remains in power-off mode as long as a switch-on event doesn’t occur
(i.e. a low level on the
PWR_ON
pin, or an RTC alarm, or a charger detection), and enters not-powered mode if
the supply is removed from the
VCC
pin.
To avoid an increase of module current consumption in power-down mode, any external signal
connected to the module digital pins (UART interface, Digital audio interface, HS_DET, GPIOs) must be
tri-stated when the module is in the not-powered or power-off modes. If the external signals connected
to the module digital pins cannot be set low or tri-stated, insert a switch (e.g. Texas Instruments
SN74CB3Q16244, or Texas Instruments TS5A3159, or Texas Instruments TS5A63157) between the two-
circuit connections. Set the switch to high impedance when the module is in power-down mode (to
avoid an increase of the module power consumption).
Figure 20 describes the power-off sequence.
VCC
V_BCKP
PWR_ON
*
LDOs
RESET_N
System State
BB Pads State
Operational
OFF
Tristate / Floating
ON
Operational
→
Tristate / Floating
AT+CPWROFF
sent to the module
0 ms
~50 ms
~400 ms
OK
replied by the module
Figure 20: Power off sequence description (* - the PWR_ON signal state is not relevant during this phase)
