Ublox LISA-U1 Series System Integration Manual

Also see for LISA-U100: Integration manual

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Ublox LISA-U1 Series System Integration Manual Manual pdf 25 page image

LISA-U1 series - System Integration Manual3G.G2-HW-10002-3 Preliminary System descriptionPage 25 of 1251.5.3 Current consumption profilesDuring operation, the current drawn by the LISA-U1 series modules through the VCC pins can vary by severalorders of magnitude. This ranges from the high peak of current consumption during GSM transmitting bursts atmaximum power level in 2G connected mode, to continuous high current drawn in UMTS connected mode, tothe low current consumption during power saving in idle mode.1.5.3.1 2G connected modeWhen a GSM call is established, the VCC consumption is determined by the current consumption profile typicalof the GSM transmitting and receiving bursts.The current consumption peak during a transmission slot is strictly dependent on the transmitted power, whichis regulated by the network. If the module is transmitting in GSM talk mode in the GSM 850 or in the E-GSM900 band and at the maximum RF power control level (approximately 2 W or 33 dBm in the allocated transmitslot/burst) the current consumption can reach up to 2500 mA (with a highly unmatched antenna) 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 1/8duty cycle according to GSM TDMA (Time Division Multiple Access).During a GSM call, current consumption is in the order of 100-200 mA in receiving or in monitor bursts and isabout 30-50 mA in the inactive unused bursts (low current period). The more relevant contribution to determinethe average current consumption is set by the transmitted power in the transmit slot.An example of current consumption profile of the data module in GSM talk mode is shown in Figure 10.Time [ms]RXslotunusedslotunusedslotTXslotunusedslotunusedslotMONslotunusedslotRXslotunusedslotunusedslotTXslotunusedslotunusedslotMONslotunusedslotGSM frame4.615 ms(1 frame = 8 slots)Current [A]200 mA~125 mA2500 mAPeak currentdepends onTX powerGSM frame4.615 ms(1 frame = 8 slots)1.51.00.50.02.52.0~125 mA ~25 mAFigure 10: VCC current consumption profile versus time during a GSM call (1 TX slot, 1 RX slot), with VCC=3.8 VWhen a GPRS connection is established there is a different VCC current consumption profile also determined bythe transmitting and receiving bursts. In contrast to a GSM call, during a GPRS connection more than one slotcan be used to transmit and/or more than one slot can be used to receive. The transmitted power depends onnetwork conditions, which set the peak current consumption, but following the GPRS specifications themaximum transmitted RF power is reduced if more than one slot is used to transmit, so the maximum peak ofcurrent consumption is not as high as can be in case of a GSM call.If the module transmits in GPRS class 12 connected mode in the GSM 850 or in the E-GSM 900 band at themaximum power control level (27 dBm typical transmitted power in the transmit slot/burst), the currentconsumption can reach up to 1400 mA (with unmatched antenna). This happens for 2.307 ms (width of the 4transmit 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 GSM TDMA.