Specifications

TC35 / TC37 Hardware Interface Description
TC35_37_HD_02_V03.10 - Released Page 35 of 92 21.12.2001
3.3.4.3 Automatic shutdown
To ensure proper operation of all assemblies under varying conditions, such as temperature,
input voltage, transmission power etc., the GSM engine features protection elements for
automatic shutdown.
Automatic shutdown takes effect if
• the PCB is exceeding the critical limits of overtemperature or undertemperature
• the battery is exceeding the critical limits of overtemperature or undertemperature.
• in a battery application, undervoltage is detected
• overvoltage is detected.
The automatic shutdown procedure is equivalent to the power-down initiated with the
AT^SMSO command, i.e. the GSM engine logs off from the network and the software enters
a secure state avoiding loss of data (except for overvoltage shutdown).
Alert messages transmitted before the device switches off are implemented as Unsolicited
Result codes (URCs). Please note that these URCs will be generated only if the function was
enabled before. To do this, use the AT^SBC and AT^SCTM commands. For detailed
instructions refer to the "TC3x AT Command Set". If disabled (factory setting), no URCs will
be sent, though the device turns off as necessary.
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 3.2.2. The values detected by either NTC resistor are measured
directly on the board and the battery and therefore, are not identical with the ambient
temperature. Use the AT^SCTM write command to enable or disable the URCs.
Proceeding from the measured temperature, TC35/TC37 sends an alert (if enabled) and
switches off when exceeding the critical limits. Please refer to Chapters 3.2.2.1 and 6 for
maximum ratings and excessive temperature. Environmental conditions are summarized in
Table 9.
• 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.
• URCs indicating the alert level "2" or "-2" are followed by immediate shutdown. If
AT^SCTM=0 (URCs disabled) you will not be informed before the module shuts down.
Table 8: Temperature dependent behaviour
Sending temperature alert
^SCTM_A: 1 Caution: Battery close to overtemperature limit.
^SCTM_B: 1 Caution: TC35/TC37 board close to overtemperature limit.
^SCTM_A: -1 Caution: Battery close to undertemperature limit.
^SCTM_B: -1 Caution: TC35/TC37 board close to undertemperature limit.
Automatic shutdown
^SCTM_A: 2 Alert: Battery beyond overtemperature limit. Module switches off.
^SCTM_B: 2 Alert: TC35/TC37 board beyond overtemperature limit. Module switches off.
^SCTM_A: -2 Alert: Battery below undertemperature limit. Module switches off.
^SCTM_B: -2 Alert: TC35/TC37 below undertemperature limit. Module switches off.