TOBY-L4 series - System Integration Manual
UBX-16024839 - R04
System description
Page 25 of 143
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 the network conditions, which set the peak current
consumption, but following the 3GPP specifications, the maximum Tx 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 the case with a 2G single-slot call.
If the module transmits in GPRS class 12 in the 850 or 900 MHz bands, at the maximum RF power control level,
the current consumption can reach a quite high peak but lower than the one achievable in 2G single-slot mode.
This happens for 2.307 ms (width of the 4 transmit slots/bursts) with a periodicity of 4.615 ms (width of 1 frame
= 8 slots/bursts), so with a 1/2 duty cycle, according to 2G TDMA.
If the module is in GPRS connected mode in the 1800 or 1900 MHz bands, the current consumption figures are
quite less high than the one in the low bands, due to 3GPP transmitter output power specifications.
Figure 6 reports the current consumption profiles in GPRS class 12 connected mode, in the 850 or 900 MHz
bands, with 4 slots used to transmit and 1 slot used to receive.
It must be noted that the actual current consumption of the module in 2G connected mode depends also on the
specific concurrent activities performed by the integrated CPU, beside the actual Tx power and antenna load.
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]
200mA
60-130mA
Peak current depends
on TX power and
actual antenna load
GSM frame
4.615 ms
(1 frame = 8 slots)
1600 mA
0.0
1.5
1.0
0.5
2.0
2.5
Figure 6: VCC current consumption profile during a 2G GPRS/EDGE multi-slot connection (4 TX slots, 1 RX slot)
For EDGE connections, the VCC current consumption profile is very similar to the GPRS current profile, so the
image shown in Figure 6, representing the current consumption profile in GPRS class 12 connected mode, is
valid for the EDGE class 12 connected mode as well.