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LTE Standard Module Series
EC25 Series Hardware Design
EC25_Series_Hardware_Design 44 / 134
array, and place these capacitors close to VBAT_BB/VBAT_RF pins. The main power supply from an
external application has to be a single voltage source and can be expanded to two sub paths with star
structure. The width of VBAT_BB trace should be no less than 1 mm; and the width of VBAT_RF trace
should be no less than 2 mm. In principle, the longer the VBAT trace is, the wider it will be.
In addition, in order to avoid the damage caused by electric surge and ESD, it is suggested that a TVS
diode with suggested low reverse stand-off voltage V
RWM
4.5 V, low clamping voltage V
C
and high reverse
peak pulse current I
PP
should be used. The following figure shows the star structure of the power supply.
Module
VBAT_RF
VBAT_BB
VBAT
C1
100uF
C6
100nF
C7
33pF
C8
10pF
+
+
C2
100nF
C5
100uF
C3
33pF
C4
10pF
D1
WS4.5D3HV
Figure 8: Star Structure of the Power Supply
3.6.3. Reference Design for Power Supply
Power design for the module is very important, as the performance of the module largely depends on the
power source. The power supply should be able to provide sufficient current up to 2.0 A at least. If the
voltage drop between the input and output is not too high, it is suggested that an LDO should be used to
supply power for the 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 the power supply.
The following figure shows a reference design for +5.0 V input power source. The typical output of the
power supply is about 3.8 V and the maximum load current is 3.0 A.