> 2.1 | Power Consumption for GSM/GPRS/EDGE

> Due to the maximum RF power levels of approx. 2W the power supply current is modulated with 2A (approx.) pulses of 0.577ms every 4.6ms. During the receive only time period, current GSM call consumption is lower than 100mA. An example current profile is illustrated in Figure 1.
> The measured values refer to the GSM 900MHz band at maximum power level with a real 50Ohm load. These values may increase up to 2...3A with an antenna connected depending on its mismatch.
> Figure 1: Current peaks in GSM talk mode (example)
> During a GSM call the module transmits in one timeslot, receives in one or two timeslots and is idle for 5-6 timeslots. In all it transmits for 577 μs and is idle or receiving for 4.03ms.
> Taking worst case figures (3A bursts) into account, this adds up to an average current consumption of about 500mA for 1Tx timeslot at GSM.
> In case the module supports GPRS Class 10, it can transmit two timeslots during one frame (receive only in 3 timeslots). Recalculating the average current consumption for a worst case GPRS Class 10 scenario, this adds up to an average power consumption of 800 mA.
> The same calculation can be done for GPRS Class 12, with the exception that the output power is reduced. This also reduces the maximum peak current, but the average supply current can rise up to 1.2A.
> The power supply requirements for EDGE are similar to the corresponding GPRS class, but the current consumption is lower.
> To give you an idea Table 1 lists current consumption values for the Siemens wireless module TC65.

> Table 1: | Typical and maximum current consumption for Siemens TC65

> Parameter | Description | Conditions | Min | Typ | Max | Unit
> I BATT+ | Average supply current | TALK mode: EGSM 900/GSM 850 GSM 1800/1900 |  | 330 295 | 510 360 | mA
> DATA mode: GPRS Class 8, (4 Rx, 1 Tx) EGSM 900/GSM 850 GSM 1800/1900 |  | 360 330 | 540 395 | mA
> DATA mode: GPRS Class 10, (3 Rx, 2 Tx) EGSM 900/GSM 850 GSM 1800/1900 |  | 540 430 | 905 650 | mA
> DATA mode: GPRS Class 12, TC65 only, with reduced power out (1 Rx, 4 Tx) EGSM 900/GSM 850 GSM 1800/1900 |  | 680 520 | 1200 800 | mA
> Peak supply current (during transmission slot every 4.6ms) | Power control level PCL 5 |  | 1.75 | 3.2 | A

> Typical values in the above table apply at an optimal 50Ohm antenna match. Maximum values apply at total antenna mismatch. A power supply design for a GSM/GPRS module should be able to deliver 540mA for 1Tx timeslot in average, while also being handle very short bursts with current consumption of up to 3.2A.