Reference Design For Power Supply - Quectel SC20-WL Hardware Design

Smart Wi-Fi Module Series
SC20-WL Hardware Design
Input current
3.8V
Voltage
3.1V
Figure 3: Voltage Drop Sample
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 should also be reserved due to its ultra-low ESR. It is
recommended to use a ceramic capacitor (100nF) for the VBAT pins. The width of VBAT_BB trace should
be no less than 1mm. In principle, the longer the VBAT trace is, the wider it will be.
In addition, in order to get a stable power source, it is suggested to use a 0.5W zener diode and place it
as close to the VBAT pins as possible. The following figure shows the star structure of the power supply.
VBAT
VBAT_BB
+
C2
C1
D1
100nF
100uF
Module
Figure 4: Power Supply

3.4.3. Reference Design for Power Supply

The power design for the module is very important, as the performance of module largely depends on the
power source. The power supply of SC20-WL should be able to provide sufficient current up to 3A at least.
If the voltage drop between the input and output is not too high, it is suggested to use an LDO 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.
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