User's Manual

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Note d’étude / Technical document : URD1 – 5625.1 – 006 / 69796 Edition 03
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3.8.3 Backup Battery technology recommended
3.8.3.1 Manganese Silicon Lithium-Ion rechargeable Battery
Sagem does not recommend to use this kind of technology because of the following drawbacks:
• the maximum discharge current is limited (Shall be compliant with the module characteristics)
• the over-discharge problem: most of the Lithium Ion rechargeable batteries are not able to recover their
charge when their voltage reaches a low-level voltage. To avoid this, it is necessary to add a safety
component to disconnect the backup battery in case of over–discharge condition. In such a case, this
implementation is too complicated (too much components for that function).
• The charging current has to be regulated
SAGEM does not recommend to use this kind of backup battery technology at all.
3.8.3.2 Capacitor Battery
These kinds of backup battery have not the drawbacks of the Lithium Ion rechargeable battery.
As there are only capacitors:
• the maximum discharge current is generally bigger,
• there is no problem of over-discharge: the capacitor is able to recover its full charge even if its voltage has
previously fallen to 0V.
• there is no need to regulate the charging current.
Moreover, this kind of battery is available in the same kind of package than the Lithium Ion cell and fully
compatible on a mechanical point of view. The only disadvantage is that the capacity of this kind of battery is
significantly smaller than Manganese Silicon Lithium Ion battery. But for this kind of use (supply internal RTC
when the main battery is removed), the capacity is generally enough.
SAGEM strongly recommends to use this kind of backup battery technology.
3.9 General Purpose Input Output
Ten General Purpose Input Output (GPIO) are available on the board to board connector. The customer
application can directly use them through the appropriate AT command as :
- output : pin is set to High or Low state
- input : pin is read on request and answer is given to the customer application.
As input, different cases are possible to cover the maximum possible of customer application :
- synchronous answer to the AT command (*)
- Asynchronous answer to the AT command. The customer application previously to the request has
configured the GPIO to react on falling/rising edges. The customer application is notified asynchronously by
AT command answer when the configured trigger occurs.
(*) : AT command process is not dedicated to real-time process. Then, driving the GPIO through this AT
command is not aimed to emulated fast transient signals.
All details to drive GPIO are given in AT commands document [ 2 ].
3.10 Temperature sensor
One temperature sensor is available on the MO300 module. Its is located on the MO300 PCB (near the board
to board connector) and not under the MO300 shield in order to give the ambient temperature of the customer
application.
Due to the fast react and sensitivity of the temperature sensor, the result can be more or less accurate
depending on possible draughts affecting the sensor. To give more precise results, the temperature sensor
must be , as far as possible, isolated from draughts in the customer design.
The temperature sensor covers all the operational temperature range of the MO300 module.
The temperature can be read on request through appropriate AT commands as described in AT commands
document [ 2 ].