MC45 Hardware Interface Description
P R E L I M I N A R Y
MC45_HD_01_V00.02a
Page 43 of 90
12.08.2002
Table 11: Temperature dependent behaviour
Sending temperature alert (15 s after start-up, otherwise only if URC presentation enabled)
^SCTM_A: 1
Caution: T
amb
of battery close to overtemperature limit.
^SCTM_B: 1
Caution: T
amb
of board close to overtemperature limit.
^SCTM_A: -1
Caution: T
amb
of battery close to undertemperature limit.
^SCTM_B: -1
Caution: T
amb
of board close to undertemperature limit.
^SCTM_A: 0
Battery back to uncritical temperature range.
^SBCTM_B: 0
Board back to uncritical temperature range.
Automatic shutdown (URC appears no matter whether or not presentation was enabled)
^SCTM_A: 2
Alert: T
amb
of battery equal or beyond overtemperature limit. MC45 switches off.
^SCTM_B: 2
Alert: T
amb
of board equal or beyond overtemperature limit. MC45 switches off.
^SCTM_A: -2
Alert: T
amb
of battery equal or below undertemperature limit. MC45 switches off.
^SCTM_B: -2
Alert: T
amb
of board equal or below undertemperature limit. MC45 switches off.
The values stated in Table 11 are based on test conditions according to IEC 60068-2-2 (still
air).
3.3.4.2 Undervoltage shutdown if battery NTC is present
In applications where the module’s charging technique is used and an NTC is connected to
the BATT_TEMP terminal, the software constantly monitors the applied voltage to check that
the battery voltage is sufficient to set up a call. When the battery voltage decreases to
V
BATT+
<3.6V, the following URC will be presented:
^SBC: Undervoltage
To enable or disable the URC use the AT^SBC command. The URC will be enabled when
you enter the write command and specify the power consumption of your GSM application.
Step by step instructions are provided in [1].
The message will be reported, for example, when you attempt to set up a call while the
voltage is close to the critical limit and further power loss is caused during the transmit burst.
To remind you that the battery needs to be charged soon, the URC appears several times
before the module switches off.
3.3.4.3 Undervoltage shutdown if no battery NTC is present
The undervoltage protection is also effective in applications, where no NTC connects to the
BATT_TEMP terminal. Thus, you can take advantage of this feature even though the
application handles the charging process or MC45 is fed by a fixed supply voltage. All you
need to do is executing the write command AT^SBC=<current> which automatically enables
the presentation of URCs. You do not need to specify <current>.
Please note, that in contrast to applications with an NTC connected to BATT_TEMP, the
module will present the URC
^SBC: Undervoltage
only once and will then switch off without sending any further messages.
