UMTS/HSPA+ Module Series
UC200A-GL_Hardware_Design 28 / 78
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3.4.3. Requirements for Voltage Stability
The power supply range of the module is from 3.4 V to 4.5 V. Please make sure the input voltage will
never drop below 3.4 V.
VBAT
Ripple
Drop
Burst
Transmission
Burst
Transmission
Figure 7: Power Supply Limits during Burst Transmission
To decrease voltage drop, a bypass capacitor of about 100 µF with low ESR (ESR = 0.7
Ω
) should be
used, and a multi-layer ceramic chip (MLCC) capacitor array should also be reserved due to its ultra-low
ESR. It is recommended to use three ceramic capacitors (100 nF, 33 pF, 10 pF) for composing the MLCC
array, and place these capacitors close to the VBAT_BB and VBAT_RF pins. 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_BB trace should be no less than 1 mm; and the width of VBAT_RF trace
should be no less than 2 mm. In principle, the longer the VBAT trace is, the wider it will be.
In addition, in order to ensure the stability of power source, it is suggested that a TVS diode of which
reverse stand-off voltage is 4.7 V and peak pulse power is up to 2550 W should be used. The following
figure shows the star structure of the power supply.
1. If you use the module that does not support the GSM band, a power supply capable of providing at
least 2 A can be used in the design.
2. It is recommended to design switch control for power supply.
NOTE