User's Manual
Table Of Contents
- Copyright
- Attention
- Trademark
- Versions
- Applicable Model List
- Foreword
- Product Overview
- Structure
- Hardware Introduction
- Hardware Interface
- Electrical and Environmental Characteristic
- RF Interface
L811-EA Module Hardware User Manual Page
25
of
43
Parameters
Minimum Value
Typical Value
Maximum Value
Unit
VSD2_1V8
1.7135
1.8
1.8865
V
V
IH
0.7* VSD2_1V8
1.8
1.8865
V
V
IL
-0.3
0
0.3* VSD2_1V8
V
5.1.3 VRTC
VRTC is the power supply for the internal RTC of the module. In order to let RTC work for a certain time
when lost the VBAT power, as the backup power, it is recommended to add a big capacitor at the VRTC
pin.
The voltage range of the VRTC as shown in the following tables:
Parameters
Minimum Value
Recommended Value
Maximum Value
Unit
RTC working voltage
0.4
1.8
1.89
V
Voltage of VRTC
RTC Current Consumption
0.4V ~ 1V
1 uA
1V ~ 1.89V
2 uA
The reference design of VRTC circuit shown as follows:
Figure 5- 1 VRTC Reference Design
Note:
R8 is a current-limiting resistor, used to ensure the VRTC works properly and free from being affected
by peripheral circuits. R8 ≥ 1k Ohm.
The current consumption is about 2A when 1.8V VRTC is supplied from the external capacitor.
The value of C9 will affect the retaining time of RTC after VBAT is lost. The remaining time of RTC
can be roughly calculated by the following formula: