SARA-G450 - System integration manual
UBX-18046432 - R08 System description Page 18 of 143
C1-Public
When a GPRS connection is established, more than one slot can be used to transmit and/or more than
one slot can be used to receive. The transmitted power depends on network conditions, which set the
peak current consumption, but following the GPRS specifications the maximum transmitted RF
power is reduced if more than one slot is used to transmit, so the maximum peak of current is not as
high as can be in the case of a GSM transmission.
If the module transmits in GPRS multi-slot class 10 or 12, in 850 or 900 MHz bands, at maximum RF
power level, the consumption can reach a quite high peak but lower than the one achievable in 2G
single-slot mode. This happens for 1.154 ms (width of the 2 Tx slots/bursts) in the case of multi-slot
class 10 or for 2.308 ms (width of the 4 Tx slots/bursts) in the case of multi-slot class 12, with a
periodicity of 4.615 ms (width of 1 frame = 8 slots/bursts), so with a 1/4 or 1/2 duty cycle, according to
GSM TDMA.
If the module is in GPRS connected mode in the 1800 or 1900 MHz bands, consumption figures are
lower than in the 850 or 900 MHz band because of the 3GPP Tx power specifications.
Figure 6 illustrates the current consumption profiles in GPRS connected mode, in the 850 or 900 MHz
bands, with 2 slots used to transmit and 1 slot used to receive, as for the GPRS multi-slot class 10.
Time [ms]
RX
slot
unused
slot
unused
slot
TX
slot
TX
slot
unused
slot
MON
slot
unused
slot
RX
slot
unused
slot
unused
slot
TX
slot
TX
slot
unused
slot
MON
slot
unused
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
Current [A]
60-120mA
GSM frame
4.615 ms
(1 frame = 8 slots)
1.5
1.0
0.5
0.0
60-120mA
10-40mA
200mA
Peak current depends
on TX power and
actual antenna load
1600 mA
Figure 6: VCC current consumption profile versus time during a GPRS multi-slot class 10 connection (2 TX slots, 1 RX slot)
Figure 7 illustrates the current consumption profiles in GPRS connected mode, in the 850 or 900 MHz
bands, with 4 slots used to transmit and 1 slot used to receive, as for the GPRS multi-slot class 12.
Time [ms]
RX
slot
unused
slot
TX
slot
TX
slot
TX
slot
TX
slot
MON
slot
unused
slot
RX
slot
unused
slot
TX
slot
TX
slot
TX
slot
TX
slot
MON
slot
unused
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
Current [A]
60-120mA
GSM frame
4.615 ms
(1 frame = 8 slots)
1.5
1.0
0.5
0.0
60-120mA
10-40mA
200mA
Peak current depends
on TX power and
actual antenna load
1600 mA
Figure 7: VCC current consumption profile versus time during a GPRS multi-slot class 12 connection (4 TX slots, 1 RX slot)
For detailed current consumption values, see the SARA-G450 data sheet [1].
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