EES3 Hardware Interface Description
3.3 Power Up / Power Down Scenarios
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EES3_HD_v01.100b
Page 38 of 118
2009-08-12
Confidential / Released
3.3.4.2
Deferred Shutdown at Extreme Temperature Conditions
In the following cases, automatic shutdown will be deferred if a critical temperature limit is ex-
ceeded:
•
While an emergency call is in progress.
•
During a two minute guard period after power-up. This guard period has been introduced in
order to allow for the user to make an emergency call. The start of emergency call extends
the guard period until the end of the call. Any other network activity may be terminated by
shutdown upon expiry of the guard time. The guard period starts again when the module
registers to the GSM network the first time after power-up.
If the temperature is still out of range after the guard period expires or the call ends, the module
switches off immediately (without another alert message).
CAUTION! Automatic shutdown is a safety feature intended to prevent damage to the module.
Extended usage of the deferred shutdown functionality may result in damage to the module,
and possibly other severe consequences.
3.3.4.3
Undervoltage Shutdown
If the measured battery voltage is no more sufficient to set up a call the following URC will be
presented:
^SBC: Undervoltage.
The message will be reported, for example, when you attempt to make a call while the voltage
is close to the shutdown threshold of 3.2V and further power loss is caused during the transmit
burst. In IDLE mode, the shutdown threshold is the sum of the module’s minimum supply volt-
age (3.2V) and the value of the maximum voltage drop resulting from earlier calls. This means
that in IDLE mode the actual shutdown threshold may be higher than 3.2V. Therefore, to prop-
erly calculate the actual shutdown threshold application manufacturers are advised to measure
the maximum voltage drops that may occur during transmit bursts.
To remind you that the battery needs to be charged soon, the URC appears several times be-
fore the module switches off.
This type of URC does not need to be activated by the user. It will be output automatically when
fault conditions occur.
