Telit GE863-QUAD / GE863-PY
Hardware User guide
1vv0300697, Rev. ISSUE#0, - 21/11/05
Reproduction forbidden without Telit Communication written authorization – All Right reserved – Right of modification reserved
page 10 of 69
3 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.
3.1Power Supply Requirements
The GE863-QUAD 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):
1.9 A
• Max Average current consumption during GPRS transmission (rms):
500 mA
• Max Average current consumption during VOICE/CSD transmission (rms):
270 mA
• Average current during Power Saving:
≈ 4 mA
• Average current during idle (Power Saving disabled)
≈ 19 mA
The GSM system is made in a way that the RF transmission is not continuous, else it is packed
into bursts at a base frequency of about 216 Hz, 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.
3.2 General Design Rules
The principal guidelines for the Power Supply Design embrace three different design steps:
- the electrical design
- the thermal design.
- the PCB layout.
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