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UMTS/HSPA Module Series

UC20 Hardware Design

UC20_Hardware_Design Confidential / Released 29 / 82

< 400mV

Current

VBAT

≤ 2.0A

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

100uF

100nF

33pF

10pF

100nF

100uF

33pF

10pF

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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