UMTS/HSPA Module Series
UG96 Hardware Design
UG96_Hardware_Design 27 / 76
59, 61, 62,
67~74,
79~82,
89~91,
100~102
3.6.2. Decrease Voltage Drop
The power supply range of the module is 3.3V~4.3V. Please make sure that the input voltage will never
drop below 3.3V. If the voltage drops to below 3.3V, the module will be turned off automatically. The
following figure shows the voltage drop during burst transmission in 2G network. The voltage drop will be
less in 3G and 4G networks.
<400mV
Current
VBAT
≤
2.0A
Burst
Transmission
Burst
Transmission
Min. 3.3V
Figure 6: Voltage Drop during Burst Transmission
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 (MLCC) capacitor 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_BB/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 1mm, and the width of VBAT_RF trace should be no
less than 2mm. 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 that a zener diode whose dissipation
power is more than 0.5W should be used. The following figure shows the star structure of the power
supply.
