Buck Circuit Pins Introduction - Quectel FC908A Hardware Design

3.4.2. Buck Circuit Pins Introduction

The following table describes the pin definition of the internal buck circuit of the module:
Table 6: Definition of Buck Circuit Pins
Pin Name Pin No.
VIN_LDO_OUT 21
VIN_LDO 23
GND 20
VIN_LDO_OUT/VIN_LDO is the output and input pins of the buck circuit inside the module, and pin 20 is
the dedicated GND pin of the buck circuit. Because the buck circuit is prone to high-frequency noise,
special attention shall be paid to it. It is recommended to use 2.2 μH inductors such as
TFM201610ALM-2R2MTAA (TDK) and 4.7 μF capacitors to ensure that the traces are as short as
possible and the trace width shall not be less than 0.4mm. At the same time, it is recommended to route
the wires away from sensitive signals.
The following is the buck circuit reference circuit and inductance parameter recommendation table:
Table 7: Recommended Inductance Parameters
Parameter
Inductance
Tolerance
FC908A_Hardware_Design
Description
Internal buck output for the module
Internal buck input for the module
Buck circuit dedicated GND pin
Figure 4: Recommended Reference Design Circuit
Wi-Fi&Bluetooth Module Series
Recommend
2.2
± 20 %
Min. Typ.
- -
- 1.35
Unit
μH
/
Max.
-
-
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