GE863-PRO3 Hardware User Guide
1vv0300773a Rev. 0 - 24/01/08
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 24 of 64
GSM TX and RX mode
GSM Sending data mode Min power level 78,0
Max power level 200,0
GPRS (class 10) TX and RX mode
GPRS Sending data mode Min power level 124,0
Max power level 371,0
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.
POWER SUPPLY
Nominal Supply Voltage 3.8 V
Operating Supply voltage range 3.4 V - 4.2 V
Absolute Maximum voltage range 3.30 – 4.5 V
GE863-PRO
3
Mode Typical Average (mA) Mode description
Off < 2 μA (TBD)
Full Speed 140 (TBD) ARM is operational at full speed 200MHz CPU Clock , Main Clock
100 MHz and all peripherals active
Slow Clocking 1 (TBD) ARM is running on slow clock with peripherals disabled
5.3 VRTC Backup supply The RTC of the GSM/GPRS engine and the RTC & Shutdown controller of the ARM part are supplied
by VRTC. This voltage supply is generated by a low quiescent current regulator inside the module that
takes its power from VBATT pins. Since this voltage supply is needed to correctly boot the ARM part,
if it is planned to remove the VBATT supply and still turn on the ARM part supplied by VBATT2, then
an appropriate power supply must be provided to the VRTC pin.
To obtain several working years for the Real Time Clock of the GSM/GPRS engine and the RTC,
32KHz oscillator & Shutdown controller of the ARM part without VBATT power supply voltage, it is
needed to make use of a lithium primary battery to supply the RTC circuits in the Telit Module.
The operative voltage for VRTC is lower than the voltage of primary lithium battery (3V nominal).
It is therefore necessary to put a LDO voltage regulator in the circuit.