Gemalto Cinterion ELS81-US, Hardware Interface Description

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Cinterion
®
ELS81-US Hardware Interface Description
3.2 Power Up/Power Down Scenarios
77
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els81-us_hid_v01.004 2017-09-27
Confidential / Preliminary
Page 55 of 107
3.2 Power Up/Power Down Scenarios
In general, be sure not to turn on ELS81-US while it is beyond the safety limits of voltage and
temperature stated in
Section 2.1.2.1 . ELS81-US immediately switches off after having started
and detected these inappropriate conditions. In extreme cases this can cause permanent dam-
age to the module.
3.2.1 Turn on ELS81-US
ELS81-US can be turned on as described in the following sections:
•
Connecting the operating voltage BATT+ (see Section 3.2.1.1 ).
• Hardware driven switch on by ON line: Starts Normal mode (see Section 3.2.1.2 ).
After startup or restart, the module will send the URC ^SYSSTART that notifies the host appli-
cation that the first AT command can be sent to the module (see also
[1] ).
3.2.1.1 Connecting ELS81-US BATT+ Lines
Figure 29 shows sample external application circuits that allow to connect (and also to tempo-
rarily disconnect) the module‘s BATT+ lines from the external application‘s power supply.
Figure 29 illustrates the application of power employing an externally controlled microcontrol-
ler. The voltage supervisory circuit ensures that the power is disconnected and applied again
depending on given thresholds.
The transistor T2 mentioned in Figure 29 should have an R
DS_ON
value
<
50m
Ω
in order to min-
imize voltage drops.
Such circuits could be useful to maximize power savings for battery driven applications or to
completely switch off and restart the module after a firmware update.
After connecting the BATT+ lines the module can then be (re-)started as described in Section
3.2.1.2 and Section 3.2.2 .