UMTS/HSPA(+) Module Series
UC200T-EM Hardware Design
UC200T-EM_Hardware_Design 24 / 68
3.5.2.
Decrease Voltage Drop
The power supply range of the module is from 3.4V to 4.3V. Please make sure that the input voltage will
never drop below 3.4V. The following figure shows the voltage drop during burst transmission in 2G
network. The voltage drop will be less in 3G networks.
VBAT
Burst
Transmission
Min.3.3V
Ripple
Drop
Burst
Transmission
Figure 3: Power Supply Limits during Burst Transmission
To decrease voltage drop, a bypass capacitor of about 100µF with low ESR 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 the VBAT 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 TVS diode WS4.5D3HV of which
reverse stand-off voltage is 4.7V and peak pulse power is up to 2550 Watts should be used. The following
figure shows the star structure of the power supply.
Module
VBAT_RF
VBAT_BB
VBAT
C1
100uF
C6
100nF
C7
33pF
C8
10pF
+
+
C2
100nF
C5
100uF
C3
33pF
C4
10pF
D1
WS4.5D3HV
Figure 4: Star Structure of the Power Supply
56, 72, 85~112