LTE Standard Module Series
EC200U_Series_Hardware_Design 32 / 94
To decrease voltage drop, a bypass capacitor of about 100 µF with low ESR (ESR = 0.7
Ω) should be
used, and a multi-layer ceramic chip (MLCC) capacitor array should also be reserved due to its ultra-low
ESR. It is recommended to use three ceramic capacitors (100 nF, 33 pF, 10 pF) for composing the MLCC
array, and place these capacitors close to VBAT_BB and VBAT_RF. 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
configuration routing. The width of VBAT_BB trace should be no less than 2 mm; and the width of
VBAT_RF trace should be no less than 2.5 mm. In principle, the longer the VBAT trace is, the wider it will
be.
In addition, in order to ensure the stability of power source, it is suggested that a TVS diode of which
reverse stand-off voltage is 4.7 V and peak pulse power is up to 2550 W should be used.
The following figure shows the star configuration routing of the power supply.
Module
VBAT_RF
VBAT_BB
VBAT
C1
100
μ
F
C6
100 nF
C7
33 pF
C8
10 pF
+
+
C2
100 nF
C5
100
μ
F
C3
33 pF
C4
10 pF
D1
WS4.5D3HV
Figure 8: Star Configuration Routing of 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 to the module that
only supports LTE network, while 3 A at least should be provided for GSM network. 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),
use a buck converter as the power supply.
The following figure shows a reference design for +5 V input power source. The typical output of the
power supply is about 3.8 V and the maximum load current is 3.5 A.
