Hardware Interface Description - KORE Telematics

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XT55/56 Hardware Interface Description Confidential / Released s 3.4 Automatic GPRS Multislot Class change Temperature control is also effective for operation in GPRS Multislot Class 10. If the board temperature increases to the limit specified for restricted operation 1) while data are transmitted over GPRS, the module automatically reverts from GPRS Multislot Class 10 (2 Tx) to Class 8 (1Tx). This reduces the power consumption and, consequently, causes the board’s temperature to decrease. Once the temperature drops to a value of 5 degrees below the limit of restricted operation, XT55/56 returns to the higher Multislot Class. If the temperature stays at the critical level or even continues to rise, XT55/56 will not switch back to the higher class. After a transition from Multislot Class 10 to Multislot 8 a possible switchback to Multislot Class 10 is blocked for one minute. Please note that there is not one single cause of switching over to a lower GPRS Multislot Class. Rather it is the result of an interaction of several factors, such as the board temperature that depends largely on the ambient temperature, the operating mode and the transmit power. Furthermore, take into account that there is a delay until the network proceeds to a lower or, accordingly, higher Multislot Class. The delay time is network dependent. In extreme cases, if it takes too much time for the network and the temperature cannot drop due to this delay, the module may even switch off as described in Chapter 3.3.3.1. 1) See Table 26 for temperature limits known as restricted operation. XT55/56_hd_v02.06a Page 40 of 125 17.12.2004
XT55/56 Hardware Interface Description Confidential / Released s 3.5 Charging control of the GSM part The GSM part of the XT55/56 module integrates a charging management for Li-Ion batteries. You can skip this chapter if charging is not your concern, or if you are not using the implemented charging algorithm. XT55/56 has no on-board charging circuit. To benefit from the implemented charging management you are required to install a charging circuit within your application. In this case, XT55/56 needs to be powered from a Li-Ion battery pack, e.g. as specified in Table 8. Note: The charging control described in this chapter is integrated in the GSM part of the XT55/56 and has been optimized for it only. When using the charging control function for the entire XT55/56 module, please consider the current consumption of the GPS part and your application. The value can be set with the AT^SBC command. This command should be used to specify the power consumption if the GSM part, the GPS part and your application are powered from the same battery. For further details refer to [1]. For using the trickle charging functionality you should design the 470R (illustrated in Figure 7) according to the current consumption of your application. The module only delivers, via its GSM_POWER line and GSM_CHARGE line, the control signals needed to start and stop the charging process. The charging circuit should include a transistor and should be designed as illustrated in Figure 7. A list of parts recommended for the external circuit is given in Table 7. Input from to GSM_POWER charger (5.5V - 8V) under load 470R 1SS355 to GSM_BATT+ PCB spark gap 4V3 Battery pack 1/ 5 ESDA6V1-5W6 SI3441DV CRS04 + NTC GSM_BATT_TEMP 100nF 10k 3k3 - 1/ 5 ESDA6V1-5W6 GSM_CHARGE Figure 7: Schematic of approved charging transistor, trickle charging and ESD protection XT55/56_hd_v02.06a Page 41 of 125 17.12.2004
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