User's Manual

UC864-G Hardware User Guide

DRAFT

- 29/10/07

5 Power Supply

The power supply circuitry and board layout are a very important part in the full product design and

they strongly reflect on the product overall performances, hence read carefully the requirements and

the guidelines that will follow for a proper design.

5.1 Power Supply Requirements

The UC864-G power requirements are:

• Nominal Supply Voltage: 3.8 V

• Max Supply Voltage: 4.2 V

• Supply voltage range: 3.4 V - 4.2 V

• Max Peak current consumption (impulsive): 1.8A

• Max Average current consumption during WCDMA transmission: 700mA

• Max Average current consumption during class 12 GPRS transmission(@4TX): 930mA

• Max Average current consumption during GPS Tracking : TBD

• Max Average current consumption during VOICE/CSD transmission: 340mA

• Average current during Power Saving (with CFUN=5) during WCDMA mode: TBD

• Average current during idle (Power Saving disabled) during WCDMA mode: TBD

• Average current during Power Saving (with CFUN=5) during GSM/GPRS mode: TBD

• Average current during idle (Power Saving disabled) during GSM/GPRS mode: 37mA

• Average GPS current during Power Saving : TBD

In GSM/GPRS mode, RF transmission is not continuous and it is packed into bursts at a base

frequency of about 216 Hz, and the relative current peaks can be as high as about 2A. Therefore the

power supply has to be designed in order to withstand with these current peaks without big voltage

drops; this means that both the electrical design and the board layout must be designed for this

current flow.

If the layout of the PCB is not well designed a strong noise floor is generated on the ground and the

supply; this will reflect on all the audio paths producing an audible annoying noise at 216 Hz; if the

voltage drop during the peak current absorption is too much, then the device may even shutdown as a

consequence of the supply voltage drop.

TIP: The electrical design for the Power supply should be made ensuring it will be capable of a peak current output

of at least 2 A.