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L811-EB Hardware User Manual Page 21 of 47
Current consumption for VRTC is about 10uA.
C1 value will affect the sustaining time for RTC clock after VBAT outage, and the sustaining time for
RTC can refer to the following formula: T = (1.8-1.0) * C / 10 = 0.08C, the unit is “second”. That is, if
C1 uses a 100uF capacitor, and the sustaining time for the RTC is approximately 8s.
If there is no need for the module clock backup feature, VRTC pin can be left floating.
3.2.3
1.8V Power Supply
The L811-EB module provides 1.8V power supply through VSD2_1V8 for the digital circuits in the module,
and the voltage is the logical voltage level for the module, which can be used to indicate the start-up
status of the module and can also be used for circuit application of external low current (<50mA), and can
be left floating if not used. The definition for the logical voltage level of VSD2_1V8 is as follows:
Parameters
Minimum Value
Typical Value
Maximum Value
Unit
VSD2_1V8
1.71
1.8
1.89
V
V
IH
1.3
1.8
1.89
V
V
IL
-0.3
0
0.5
V
3.2.4
Power Consumption
In the case of 3.8V power supply, the power consumption for L811-EB module is shown in the following
table:
Parameter
Mode
Condition
Typical
Current(mA)
I
off
Power off
Power supply,
module power off
0.086
I
Idle
GSM
MFRMS=5
12
WCDMA
DRX=8
11.8
LTE FDD
Paging cycle #256 frames (2.56 sec DRx cycle)
12
I
Sleep
GSM
MFRMS=2
3.6
MFRMS=5
3.2
MFRMS=9
2.7
WCDMA
DRX=6
2.8
DRX=8
2.5
