SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11
System description
Page 26 of 157
current consumption. But according to 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 it can be in the
case of a GSM call.
If the module transmits in GPRS multi-slot class 12, in 850 or 900 MHz bands, at maximum RF power level,
the consumption can reach a quite a high peak but lower than the one achievable in 2G single-slot mode.
This happens 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 1/2 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.
illustrates the current consumption profiles in GPRS connected mode, in 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
M ON
slot
unused
slot
RX
slot
unused
slot
TX
slot
TX
slot
TX
slot
TX
slot
M ON
slot
unused
slot
GSM f ram e
4.615 m s
(1 f ram e = 8 slot s)
Current [A]
60-120m A
GSM f ram e
4.615 m s
(1 f ram e = 8 slot s)
1.5
1.0
0.5
0 .0
60-120m A
10-40m A
20 0 m A
Peak current depends
on T X power and
act ual ant enna load
160 0 m A
Figure 7: VCC current consumption profile versus time during a GPRS multi-slot class 12 connection (4 TX slots, 1 RX slot)
In case of EGPRS (i.e. EDGE) connections, the VCC current consumption profile is very similar to the one
during GPRS connections: the current consumption profile in GPRS multi-slot class 12 connected mode
illustrated in the
is representative for the EDGE multi-slot class 12 connected mode as well.
1.5.1.4
VCC current consumption in low power deep sleep mode (PSM enabled)
The power saving mode configuration is by default disabled, but it can be enabled using the AT+CPSMS
command (see the SARA-R4/N4 series AT Commands Manual
).
When power saving mode is enabled, the module automatically enters the PSM low power deep sleep
mode whenever possible, reducing current consumption down to a steady value in the
µ
A range: only the
RTC runs with internal 32 kHz reference clock frequency.
Detailed current consumption values can be found in the SARA-R4/N4 series Data Sheet
☞
Due to RTC running during PSM mode, the Cal-RC turns on the crystal every ~10 s to calibrate the RC
oscillator, as a consequence, a very low spike in current consumption will be observed.
