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1.6.2
Cellular RTC supply input / output (V_BCKP)
When VCC voltage is within the valid operating range, the internal Power Management Unit (PMU)
supplies the Real Time Clock (RTC) of the LENA-R8 series modules' cellular subsystem, and the same
supply voltage is available on the V_BCKP pin. If the VCC voltage is under the minimum operating limit
(e.g. during not powered mode), the V_BCKP pin can externally supply the RTC of the LENA-R8 series
modules' cellular subsystem.
1.6.3
Cellular generic digital interfaces supply output (V_INT)
The V_INT output pin of the LENA-R8 series modules cellular system is connected to an internal 1.8 V
supply with a current capability specified in the LENA-R8 series data sheet [1]. This supply is
internally generated by a linear LDO regulator integrated in the Power Management Unit and it is
internally used to source the generic digital interfaces of the cellular module (as the UARTs, I2C, I2S,
GPIOs), as described in
switched on, and disabled when the cellular system is switched off.
LENA-R8 series
Power
Management
Unit
BB processor
LDO
Digital I/O
VCC
51
regulator
Interfaces
Figure 10: LENA-R8 series interfaces supply output (V_INT) simplified block diagram
1.7 Cellular system function interfaces
1.7.1
Cellular system power-on
When LENA-R8 series modules cellular system is not powered, it can be switched on as follows:
•
Apply a voltage at the VCC module supply input within the operating range (see LENA-R8 series
data sheet [1], cellular system VCC operating input voltage), and then force a low level at the
PWR_ON input pin, which is normally set high by an internal pull-up, for a valid time period (see
LENA-R8 series data sheet [1], PWR_ON input line low time to trigger cellular system switch on).
When LENA-R8 series modules cellular system is in power-off mode (switched off, with a voltage at
the VCC supply input within the normal operating range reported in LENA-R8 series data sheet [1]),
it can be switched on by:
•
Forcing a low level at the PWR_ON input pin, which is normally set high by an internal pull-up, for
a valid time period (see the LENA-R8 series data sheet [1], PWR_ON low time for switch on).
•
RTC alarm, i.e. pre-programmed scheduled time by +CALA AT command.
The PWR_ON input line is intended to be driven by open drain, open collector, or contact switch.
As described in
Figure
are different from the other generic digital interfaces as indicated in LENA-R8 series data sheet [1].
LENA-R8 series
Power
management
PWR_ON
15
Power-on/off
Figure 11: LENA-R8 series PWR_ON input description
UBX-22015376 - R02
C1-Public
Figure
10. The output of this regulator is enabled when the cellular system is
Memory
4
V_INT
11, the PWR_ON input line is internally pulled up. The input voltage thresholds
Baseband
processor
Power-on/off
System description
LENA-R8 series - System integration manual
Page 20 of 116
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