Fibocom L-831-EA, User Manual

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L831-EA Module Hardware User Manual Page 24 of 43
5 Hardware Interface
5.1 Power Interface
5.1.1 Power Supply
L831-EA module requires a 3.135V~ 4.4V DC power supply to provide the maximum GSM emission
current with 2A.
Input power supply requirements as listed below:
Parameters Minimum Recommended Maximum Unit
+3.3V 3.135 3.3 4.4 V
Note:
1. The ripple of Power supply must be lower than 200mV.
2. The minimum value of power supply voltage drops shall more than 3.135V.
The filter capacitor design of the supply circuit is as follows:
Recommended
capacitor
Application Description
330uF
Supply capacitor
Reduce power wave in call. The
value of capacitor is bigger better.
1uF,100nF
Digital signal noise
Filtering interference from clock and
digital signal.
39pF,33pF 700/850/900 MHz band
Filtering the RF reference.
18pF,8.2pF,6.8pF 1700/1800/1900,2100,2500/2600MHz band
Filtering the RF reference.
5.1.2 VSD2_1V8
VSD2_1V8 is the digital part circle`s` power supply within the module, VSD2_1V8 can use for the index
signal and the reference level. With the circle design only use for external low current application
（
<50mA
）
, and floating it if not use.
Parameters Minimum Recommended Maximum 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