Reference Design For Power Supply - Quectel UC20 Manual

VBAT
FB1
FB2
+
C1
D1
100uF
5.1V
Please pay special attention to the power supply design for applications. Make sure the input voltage will
never drop below 3.4V. If the voltage drops below 3.4V, the module will turn off automatically. The PCB
traces from the VBAT pins to the power source must be wide enough to ensure that there isn't too much
voltage drop occurs in the transmitting procedure. The width of VBAT_BB trace should be no less than
1mm, and the width of VBAT_RF trace should be no less than 2mm, and the principle of the VBAT trace is
the longer, the wider.

3.6.3. Reference Design for Power Supply

The power design for the module is very important, since the performance of power supply for the module
largely depends on the power source. The power supply is capable of providing the sufficient current up to
2A at least. If the voltage drop between the input and output is not too high, it is suggested to use a LDO
to supply power for module. If there is a big voltage difference between the input source and the desired
output (VBAT), a buck converter is preferred to be used as a power supply.
The following figure shows a reference design for +5V input power source. The designed output for the
power supply is 3.88V and the maximum load current is 3A.
DC_IN
C1
470uF 100nF
UC20_Hardware_Design
C4
C2 C3
100nF 33pF 10pF
Figure 6: Star Structure of the Power Supply
MIC29302WU
2
IN
R1
51K
C2
Figure 7: Reference Circuit of Power Supply
+
C5
C6 C7
100uF 100nF 33pF
U1
4
OUT
R2
100K
1%
470R
R3
47K
1%
Confidential / Released
UMTS/HSPA Module Series
UC20 Hardware Design
VBAT_RF
VBAT_BB
C8
10pF
Module
VBAT
C4
C3
R4
470uF 100nF
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