Smart Module Series
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3.4. Power Supply
3.4.1. Power Supply Pins
SC262R series module provides two VBAT_RF pins and two VBAT_BB pins for connection with the
external power supply. The VBAT_RF pins are used for the RF part of the module and the VBAT_BB pins
are used for the baseband part of the module.
3.4.2. Voltage Stability Requirements
The power supply range of the module is 3.55
–4.2 V, and the recommended value is 3.8 V. The power
supply performance, such as load capacity, voltage ripple, etc. directly influences the modul
e’s
performance and stability. Under ultimate conditions, the transient peak current of the module may surge
up to 3 A. If the power supply capacity is not sufficient, there will be the risk that the voltage drops below
3.1 V and as a result the module powers off automatically. Therefore, make sure the input voltage never
drops below 3.1 V.
Power
Supply (V)
Burst
Transmission
Ripple
Drop
Burst
Transmission
Load (A)
Figure 3: Power Supply Limits during Burst Transmission
To decrease voltage drop, use a bypass capacitor of about 100 µF with low ESR
(ESR = 0.7 Ω), and
reserve a multi-layer ceramic chip capacitor (MLCC) array due to its ultra-low ESR. It is recommended to
use three ceramic capacitors (100 nF, 33 pF, 10 pF) to compose the MLCC array and place these
capacitors close to VBAT_BB/VBAT_RF pins. Additionally, add a 4.7 µF capacitor in parallel. The main
power supply from an external application has to be a single voltage source and can be expanded to two
sub paths with star structure. 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.
In addition, in order to get a stable power source, it is suggested to use a TVS and place it as close to the
VBAT_BB/VBAT_RF pins as possible to enhance surge protection. The following figure shows the star
structure of the power supply.
