UMTS/HSPA Module Series
UC20 Hardware Design
UC20_Hardware_Design Confidential / Released 29 / 82
< 400mV
Current
VBAT
≤ 2.0A
burst
burst
Min. 3.3V
Figure 6: Voltage Drop during Transmitting Burst
To decrease voltage drop, a bypass capacitor of about 100µF with low ESR should be used. Multi-layer
ceramic chip (MLCC) capacitor can provide the best combination of low ESR. The main power supply
from an external application has to be a single voltage source and 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, and the principle of the VBAT trace is the longer, the wider.
Three ceramic capacitors (100nF, 33pF, 10pF) are recommended to be applied to the VBAT pins. The
capacitors should be placed close to the UC20’s VBAT pins. In addition, in order to get a stable power
source, it is suggested to use a zener diode of which reverse zener voltage is 5.1V and dissipation power
is more than 0.5W. The following figure shows 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
5.1V
Figure 7: Star Structure of the Power Supply
3.6.3. Reference Design for Power Supply
The power design for the module is very important, since the performance of power supply for the module
largely depends on the power source. The power supply is capable of providing the sufficient current up to
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