User's Manual

TOBY-R2 series - System Integration Manual
UBX-16010572 - R04 System description
Page 20 of 147
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
high peak (see the “Current consumption” section in the TOBY-R2 series Data Sheet [1]) 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 quite less high than the one in the low bands, due to 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
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 described 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)