Specifications

AC65/AC75 Hardware Interface Description
3.4 Automatic EGPRS/GPRS Multislot Class Change
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AC65_AC75_HD_v01.002 Page 40 of 117 2006-10-30
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3.4 Automatic EGPRS/GPRS Multislot Class Change
Temperature control is also effective for operation in EGPRS Multislot Class 10 (AC75 only), GPRS Multislot
Class 10 and GPRS Multislot Class 12. If the board temperature rises close to the limit specified for normal oper-
ation (see Section 5.2 for limits) while data are transmitted over EGPRS or GPRS, the module automatically
reverts:
• from EGPRS Multislot Class 10 (2Tx slots) to EGPRS Multislot Class 8 (1Tx),
• from GPRS Multislot Class 12 (4Tx slots) to GPRS Multislot Class 8 (1Tx)
• from GPRS Multislot Class 10 (2Tx slots) to GPRS Multislot Class 8 (1Tx)
This reduces the power consumption and, consequently, causes the board’s temperature to decrease. Once the
temperature drops by 5 degrees, AC65/AC75 returns to the higher Multislot Class. If the temperature stays at
the critical level or even continues to rise, AC65/AC75 will not switch back to the higher class.
After a transition from EGPRS Multislot Class 10 to EGPRS Multislot Class 8 a possible switchback to EGPRS
Multislot Class 10 is blocked for one minute. The same applies when a transition occurs from GPRS Multislot
Class 12 or 10 to GPRS Multislot Class 8.
Please note that there is not one single cause of switching over to a lower Multislot Class. Rather it is the result
of an interaction of several factors, such as the board temperature that depends largely on the ambient temper-
ature, 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 Section 3.3.4.1.
3.5 Charging Control
AC65/AC75 integrates a charging management for rechargeable Lithium Ion and Lithium Polymer batteries. You
can skip this chapter if charging is not your concern, or if you are not using the implemented charging algorithm.
The following sections contain an overview of charging and battery specifications. Please refer to [5] for greater
detail, especially regarding requirements for batteries and chargers, appropriate charging circuits, recommended
batteries and an analysis of operational issues typical of battery powered GSM/GPRS applications.
3.5.1 Hardware Requirements
AC65/AC75 has no on-board charging circuit. To benefit from the implemented charging management you are
required to install a charging circuit within your application according to the Figure 47.
3.5.2 Software Requirements
Use the command AT^SBC, parameter <current>, to enter the current consumption of the host application. This
information enables the AC65/AC75 module to correctly determine the end of charging and terminate charging
automatically when the battery is fully charged. If the <current> value is inaccurate and the application draws a
current higher than the final charge current, either charging will not be terminated or the battery fails to reach its
maximum voltage. Therefore, the termination condition is defined as: current consumption dependent on oper-
ating mode of the ME plus current consumption of the external application. If used the current flowing over the
VEXT pin of the application interface must be added, too.
The parameter <current> is volatile, meaning that the factory default (0mA) is restored each time the module is
powered down or reset. Therefore, for better control of charging, it is recommended to enter the value every time
the module is started.
See [1] for details on AT^SBC.