图5.采用TPS54260的24V到4.2V的GSM电源电路图

　　采用TPS54260开发GSM/GPRS电源

　　The input voltage supply for the GSM/GPRS module can be from 3.2 V to 4.5 V, with an average power supply current requirement of 400 mA to ~1 A. The power supply must also be able to sustain transmission pulses of 2 A to 3 A, thus considerations for excellent load regulation and low-ripple needs to be taken into account, simultaneously ensuring a highly efficient design.

　　The average current consumption depends upon the class supported by the module. The most common GPRS classes are Class 8, Class 10 and Class 12. Higher the GPRS class, the faster the data transfer rates and correspondingly it requires more number of timeslots for transmission. Class 8 uses 4 Rx and 1 Tx slot, Class 10 uses 3 Rx and 2 Tx slots and Class 12 uses 1 Rx and 4 Tx slots.

　　Thus, a GSM/GPRS Module transmits either 1/2/3 time slot(s) of 577us during a 4.6ms period, and receives or remains idle for the rest 4.0ms/3.4ms/2.3ms time depending upon whether it is GSM/GPRS Class 8, Class 10 or Class 12 module. Taking 3 A as the amplitude of transmission bursts, this leads to an average current consumption of about 400mA incase of Class 8 to ~ 1 A in case of Class 12. A power supply design for a GSM/GPRS module should be able to deliver this average current, and also handle intermittent transmission bursts with high current consumption.

　　GSM/GPRS电源系统参数: