Error! No text of specified style in document. - System Integration Manual
CDMA-2X-11004-P1
Objective Specification
System description
Page 36 of 79
40.1.1
Current consumption profiles
During operation, the current drawn by the Error! No text of specified style in document. modules
through the VCC pins can vary by several orders of magnitude. This ranges from continuous high
current drawn in CDMA connected mode, to the low current consumption during in idle mode.
40.1.1.1
3G connected mode
During a CDMA connection, the module can transmit and receive continuously due to the
Frequency Division Duplex (FDD) mode of operation with the Code Division Multiple Access
(CDMA). The current consumption depends again on output RF power, which is always regulated
by network commands. These power control commands are logically divided into a slot of 1.25 ms,
thus the rate of power change can reach a maximum rate of 800 Hz. Since transmission and
reception are continuously enabled due to FDD CDMA implemented in the 3G that differs from the
TDMA implemented in the 2G case. In the worst scenario, corresponding to a continuous
transmission and reception at maximum output power (approximately 250 mW or 24 dBm), the
current drawn by the module at the VCC pins is in the order of continuous 600-700 mA. Even at
lowest output RF power (approximately 0.01 µW or -50 dBm), the current is in the order of less than
100 mA due to module baseband processing and transceiver activity.
An example of current consumption profile of the data module in CDMA continuous transmission
mode is shown in Figure 7.
Time
[ms]
3G frame
Current [mA]
<100 mA
Depends on TX pow er
Not actual data for
illustration
1 slot
610 mA
300
200
100
0
500
400
600
700
Figure 7: VCC current consumption profile versus time during a CDMA connection, with VCC=3.8 V
When a packet data connection is established, the actual current profile depends on the amount
of transmitted packets; there might be some periods of inactivity between allocated slots where
current consumption drops about 100 mA. Alternatively, at higher data rates the transmitted power
is likely to increase due to the higher quality signal required by the network to cope with enhanced
data speed.
Comment [s2]:
I guess it is CDMA, correct?
Comment [s3]:
Is this graphic applicable to
CDMA too?