LENA-R8 series - System integration manual
UBX-22015376 - R02
System description
Page 20 of 116
C1-Public
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
. 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
. The output of this regulator is enabled when the cellular system is
switched on, and disabled when the cellular system is switched off.
BB processor
51
VCC
4
V_INT
LDO
regulator
Digital I/O
Interfaces
Power
Management
Unit
LENA-R8 series
Memory
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
, 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
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
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
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
PWR_ON
input line is internally pulled up. The input voltage thresholds
are different from the other generic digital interfaces as indicated in LENA-R8 series data sheet
Baseband
processor
15
PWR_ON
LENA-R8 series
Power-on/off
Power
management
Power-on/off
Figure 11: LENA-R8 series PWR_ON input description
