Reference Design For Power Supply - Quectel UG89 Hardware Design

To decrease voltage drop, a bypass capacitor of about 100µF with low ESR (ESR≤0.7Ω) 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 (100nF, 33pF, 10pF) for composing the MLCC array, and
place these capacitors close to the VBAT_BB and 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 a star structure.
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. 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 WS4.5D3HV
of which reverse stand-off voltage is 4.7V and peak pulse power is up to 2550W should be used. The
following figure shows the star structure of the power supply.
VBAT
D1
WS4.5D3HV

3.5.3. 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 2.0A at least to the
module. 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.
UG89_Hardware_Design
Burst
Transmission
Current
VBAT
Min. 3.3V
Figure 3: Voltage Drop during Burst Transmission
+
C4
C2 C3
C1
100nF 33pF 10pF
100uF
Figure 4: Star Structure of the Power Supply
Burst
Transmission
+
C5 C6 C7 C8
100uF 100nF 33pF 10pF
UMTS/HSPA+ Module Series
UG89 Hardware Design
≤2.0A
<400mV
VBAT_RF
VBAT_BB
Module
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