Power Supply; Power Supply Pins; Decrease Voltage Drop - Quectel Smart LTE Module Series Hardware Design

Table of Contents

164,165,16

RESERVED

6,190,191,

192，222

3.4. Power Supply

SC650T provides 3 VBAT pins,2 VDD_RF pins and 2 VPH_PWR pins. VBAT pins are dedicated for

connection with an external power supply. VDD_RF pins are designed for module's RF part, and are used

to connect bypass capacitors so as to eliminate voltage fluctuation of RF part. VPH_PWR pins are

designed for peripherals.

The power supply range of the module is from 3.55V to 4.4V, and the recommended value is 3.8V. The

power supply performance, such as load capacity, voltage ripple, etc. directly influences the module's

performance and stability. Under ultimate conditions, the module may have a transient peak current up to

3A. If the power supply capability is not sufficient, there will be voltage drops, and if the voltage drops

below 3.1V, the module will be powered off automatically. Therefore, please make sure the input voltage

will never drop below 3.1V.

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 capacitor (MLCC) 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 VBAT/VDD_RF pins. The width of VBAT trace should be no less than

3mm. 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 TVS and place it as close

to the VBAT pins as possible to increase voltage surge withstand capability. The following figure shows

SC650T_Hardware_Design

Reserved pins

Figure 2: Voltage Drop Sample

Smart LTE Module Series

SC650T Hardware Design

Keep these pins

open.

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