Automatic Shutdown; Temperature Dependent Shutdown - Siemens MC45 Manual

MC45 Hardware Interface Description
P R E L I M I N A R Y

3.3.4 Automatic shutdown

To ensure proper operation of all assemblies under varying conditions, such as temperature,
input voltage, transmission power etc., MC45 features protection elements for automatic
shutdown.
Automatic shutdown takes effect if
·
the MC45 board is exceeding the critical limits of overtemperature or undertemperature
·
the battery is exceeding the critical limits of overtemperature or undertemperature
·
undervoltage is detected
·
overvoltage is detected.
The automatic shutdown procedure is equivalent to the power-down initiated with the
AT^SMSO command, i.e. MC45 logs off from the network and the software enters a secure
state avoiding loss of data. This is not applicable to overvoltage shutdown, where power is
cut off immediately.
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 3.3.4.4 for details. For further instructions on AT
commands refer to [1].

3.3.4.1 Temperature dependent 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 Chapter 3.2.3. 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.
Proceeding from the measured temperature, MC45 sends an alert in the form of a URC and
switches off when exceeding the critical limits:
·
URCs indicating the alert level "1" or "-1" allow you to take appropriate precautions, such
as protect the module or battery from exposure to extreme conditions, or save or back up
data etc. 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 MC45. After 15 seconds operation, the presentation will be disabled, i.e.
no alert messages can be generated.
·
URCs indicating the alert level "2" or "-2" are followed by immediate shutdown. The
presentation of these URCs is always enabled, i.e. they will be output even though the
factory setting AT^SCTMC=0 was never changed.
·
When the temperature is back to normal, again a message will be delivered. In this case,
the URC indicates level "0".
Table 11 summarizes the maximum ratings and the associated URCs.
MC45_HD_01_V00.02a Page 42 of 90 12.08.2002