Automatic Shutdown; Thermal Shutdown - Siemens AC75 Hardware Interface Description

AC75 Hardware Interface Description
Strictly confidential / Preliminary

3.3.4 Automatic Shutdown

Automatic shutdown takes effect if:
•
the 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 3.5.7 for exceptions.
The automatic shutdown procedure is equivalent to the Power-down initiated with the
AT^SMSO command, i.e. 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 presentation of these URCs can be enabled or disabled with the
two AT commands AT^SBC and AT^SCTM. 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, 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 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.
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27.04.2006