User's Manual

GE865 Hardware User Guide
1vv0300799 Rev.11 – 13-07-2010
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 30 of 82
6.2 Power Consumption
The GE865 power consumptions are:
GE865
Mode
Average
(mA)
Mode description
SWITCHED OFF
Module supplied but Switched Off
Switched Off
<62uA
IDLE mode
AT+CFUN=1
16,0
Normal mode: full functionality of the module
AT+CFUN=4
16,0
Disabled TX and RX; module is not registered on the network
AT+CFUN=0 or =5
3,9
Paging Multiframe 2
2,5
Paging Multiframe 3
2,4
Paging Multiframe 4
1,5
Paging Multiframe 9
CSD TX and RX mode
GSM VOICE CALL
GSM900 CSD PL5
240
DCS1800 CSD PL0
175
GPRS (class 1) 1TX + 1RX
GPRS Sending data mode
GSM900 PL5
225
DCS1800 PL0
160
GPRS (class 10) 2TX + 3RX
GPRS Sending data mode
GSM900 PL5
420
DCS1800 PL0
290
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, 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.
NOTE:
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.