Quectel SC200K Series Instruction Manual page 37

To prevent the voltage from dropping below 3.25 V, it is recommended to connect a 100 µF tantalum
capacitor with low ESR (ESR = 0.7 Ω) as well as 100 nF, 33 pF, and 10 pF filter capacitors in parallel near
VBAT_BB and VBAT_RF pins of the module. It is also recommended that the PCB traces of VBAT should
be as short as possible and wide enough to reduce the equivalent impedance of the VBAT traces and
ensure that there will be no too large voltage drop under high current at the maximum transmission power.
The width of VBAT trace should be no less than 3 mm. In principle, the longer the VBAT trace is, the wider
it should be. Additionally, the ground plane of the power supply part should be as complete as possible.
In order to suppress the impact of power supply fluctuations and ensure the stability of the output power
supply, it is suggested to add a TVS component of at least 500 W and place it as close to the VBAT pins
as possible to enhance surge protection. The following figure shows a reference circuit.
SC200K_Series_Hardware_Design
3 A
Module input current
Voltage
Figure 5: Power Supply Voltage Drop Example
VBAT
+
C3 C4
C1 C2
D1
μ
100 nF 10 pF
100 F 33 pF
Figure 6: Reference Circuit of Power Supply
3.8 V
VBAT_RF
VBAT_BB
+
C5
C6 C7 C8
NM 100 nF 33 pF 10 pF
Smart Module Series
Module
36 / 105