SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R26 System description
Page 27 of 217
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 call.
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 11 reports 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 11: VCC current consumption profile versus time during a GPRS multi-slot class 10 connection (2 TX slots, 1 RX slot)
Figure 12 reports 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 12: 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 during 2G single-slot or multi-slot connection, see theSARA-G3 series
Data Sheet [1] and the SARA-U2 series Data Sheet [2].
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