TOBY-L4 series - System Integration Manual
UBX-16024839 - R04
System description
Page 24 of 143
1.5.1.2
VCC current consumption in 2G connected mode
When a GSM call is established, the
VCC
module current consumption is determined by the current
consumption profile typical of the GSM transmitting and receiving bursts.
The peak of current consumption during a transmission slot is strictly dependent on the RF transmitted power,
which is regulated by the network (the current base station). The transmitted power in the transmit slot is also
the more relevant factor for determining the average current consumption.
If the module is transmitting in 2G single-slot mode in the 850 or 900 MHz bands, at the maximum RF power
level (approximately 2 W or 33 dBm in the allocated transmit slot/burst) the current consumption can reach an
upper peak for 576.9 µs (width of the transmit slot/burst) with a periodicity of 4.615 ms (width of 1 frame =
8 slots/burst), so with a 1/8 duty cycle according to GSM TDMA (Time Division Multiple Access).
If the module is transmitting in 2G single-slot mode in the 1800 or 1900 MHz bands, the current consumption
figures are considerably lower than the one in the low bands, due to the 3GPP transmitter output power
specifications.
During a GSM call, current consumption is not so significantly high in receiving or in monitor bursts and is low in
the inactive unused bursts.
Figure 4 shows an example of the module current consumption profile versus time in 2G single-slot mode.
Time [ms]
RX
slot
unused
slot
unused
slot
TX
slot
unused
slot
unused
slot
MON
slot
unused
slot
RX
slot
unused
slot
unused
slot
TX
slot
unused
slot
unused
slot
MON
slot
unused
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
Current [A]
200 mA
60-120 mA
1900 mA
Peak current depends
on TX power and
actual antenna load
GSM frame
4.615 ms
(1 frame = 8 slots)
60-120 mA
10-40 mA
0.0
1.5
1.0
0.5
2.0
2.5
Figure 4: VCC current consumption profile versus time during a 2G single-slot call (1 TX slot, 1 RX slot)
Figure 5 illustrates
VCC
voltage profile versus time during a 2G single-slot call, according to the relative
VCC
current consumption profile illustrated in Figure 4.
Time [ms]
undershoot
overshoot
ripple
drop
Voltage [mV]
3.8 V
(typ)
RX
slot
unused
slot
unused
slot
TX
slot
unused
slot
unused
slot
MON
slot
unused
slot
RX
slot
unused
slot
unused
slot
TX
slot
unused
slot
unused
slot
MON
slot
unused
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
GSM frame
4.615 ms
(1 frame = 8 slots)
Figure 5: VCC voltage profile versus time during a 2G single-slot call (1 TX slot, 1 RX slot)