User's Manual

AC65/AC75 Hardware Interface Description

Confidential / Preliminary

AC65/AC75_hd_v00.372 Page 39 of 118 2006-08-03

3.3.4 Automatic Shutdown

Automatic shutdown takes effect if:

• the AC65/AC75 board is exceeding the critical limits of overtemperature or

undertemperature

• the battery is exceeding the critical limits of overtemperature or undertemperature

• undervoltage or overvoltage is detected

See Charge-only mode described in Section 3.5.6 for exceptions.

The automatic shutdown procedure is equivalent to the Power-down initiated with the

AT^SMSO command, i.e. AC65/AC75 logs off from the network and the software enters a

secure state avoiding loss of data.

Alert messages transmitted before the device switches off are implemented as Unsolicited

Result Codes (URCs). The URC presentation mode varies with the condition, please see

Chapters 3.3.4.1 to 3.3.4.5 for details. For further instructions on AT commands refer to [1].

3.3.4.1 Thermal Shutdown

The board temperature is constantly monitored by an internal NTC resistor located on the

PCB. The NTC that detects the battery temperature must be part of the battery pack circuit

as described in 3.5.3 The values detected by either NTC resistor are measured directly on

the board or the battery and therefore, are not fully identical with the ambient temperature.

Each time the board or battery temperature goes out of range or back to normal, AC65/AC75

instantly displays an alert (if enabled).

• URCs indicating the level "1" or "-1" allow the user to take appropriate precautions, such

as protecting the module from exposure to extreme conditions. The presentation of the

URCs depends on the settings selected with the AT^SCTM write command:

AT^SCTM=1: Presentation of URCs is always enabled.

AT^SCTM=0 (default): Presentation of URCs is enabled for 15 seconds time after

start-up of AC65/AC75. After 15 seconds operation, the presentation will be disabled,

i.e. no alert messages can be generated.

• URCs indicating the level "2" or "-2" are instantly followed by an orderly shutdown. The

presentation of these URCs is always enabled, i.e. they will be output even though the

factory setting AT^SCTM=0 was never changed.

The maximum temperature ratings are stated in Chapter 5.2. Refer to Table 7 for the

associated URCs.