Product Info

Smart LTE Module Series
SC650T Hardware Design
SC650T_Hardware_Design 39 / 131
RESERVED
164,165,16
6,190,191,
192，222
Reserved pins
Keep these pins
open.
3.4. Power Supply
3.4.1. Power Supply Pins
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.
3.4.2. Decrease Voltage Drop
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.
3.1V
Voltage
3.8V
Input current
3A
Figure 2: 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 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