UMTS/HSDPA Module
UC15 Hardware Design
UC15_Hardware_Design Confidential / Released 24 / 72
Figure 3: Star Structure of the Power Supply
Please pay special attention to the power supply design for applications. Make sure the input voltage will
never drop below 3.3V. If the voltage drops below 3.3V, the module will turn off automatically. The PCB
traces from the VBAT pins to the power source must be wide enough to ensure that there isn’t too much
voltage drop occurs in the transmitting procedure. 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.
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
2A at least. If the voltage drop between the input and output is not too high, it is suggested to use a LDO
as module’s power supply. If there is a big voltage difference between the input source and the desired
output (VBAT), a switcher power converter is preferred to use as a power supply.
The following figure shows a reference design for +5V input power source. The designed output for the
power supply is 3.88V and the maximum load current is 3A.
Figure 4: Reference Circuit of Power Supply
