u-blox LARA-R203 System Integration Manual page 21

1.5.1.2 VCC current consumption in 2G connected mode
When a GSM call is established, the VCC consumption is determined by the current consumption profile typical of
the GSM transmitting and receiving bursts.
The current consumption peak during a transmission slot is strictly dependent on the transmitted power, which is
regulated by the network. 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 (as in GSM talk mode) in the 850 or 900 MHz bands, at the
maximum RF power control level (approximately 2 W or 33 dBm in the Tx slot/burst), the current consumption can
reach an high peak / pulse (see LARA-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 the 3GPP transmitter output power specifications.
During a GSM call, current consumption is not so significantly high in receiving or in monitor bursts and it is low
in the bursts unused to transmit / receive.
Figure 4 shows an example of the module current consumption profile versus time in GSM talk mode.
Current [A]
2.0
1900 mA
1.5
1.0
0.5
200 mA
60-120 mA
10-40 mA
0.0
RX unused unused TX
slot slot slot slot
GSM frame
4.615 ms
(1 frame = 8 slots)
Figure 4: VCC current consumption profile versus time during a GSM call (1 TX slot, 1 RX slot)
Figure 5 illustrates VCC voltage profile versus time during a GSM call, according to the related VCC current
consumption profile described in Figure 4.
Voltage
3.8 V
(typ)
ripple
RX unused unused TX
slot slot slot slot
GSM frame
4.615 ms
(1 frame = 8 slots)
Figure 5: Description of the VCC voltage profile versus time during a GSM call (1 TX slot, 1 RX slot)
UBX-16010573 - R12
Peak current depends
on TX power and
actual antenna load
60-120 mA
unused unused MON unused RX
slot slot slot slot slot
undershoot
unused unused MON unused RX
slot slot slot slot slot
LARA-R2 series - System Integration Manual
unused unused TX unused unused
slot slot slot slot slot
GSM frame
4.615 ms
(1 frame = 8 slots)
overshoot
drop
unused unused TX unused unused
slot slot slot slot slot
GSM frame
4.615 ms
(1 frame = 8 slots)
MON unused
Time [ms]
slot slot
MON unused
slot slot
Time
System description
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