User's Manual

SARA-G3 and SARA-U2 series - System Integration Manual
Primary and secondary cells and batteries
Cells and batteries incorporated into equipment with intrinsic safety 'i' protection to potentially explosive gas
atmosphere shall conform to the requirements of the IEC 60079-0 [32] and IEC 60079-11 ATEX standards [33].
Shunt voltage limiters
For Level of Protection ‘ia’, the application of controllable semiconductor components as shunt voltage limiting
devices, for example transistors, thyristors, voltage/current regulators, etc., may be permitted if both the input
and output circuits are intrinsically safe circuits or where it can be shown that they cannot be subjected to
transients from the power supply network. In circuits complying with the above, two devices are considered to
be an infallible assembly.
For Level of Protection ‘ia’, three independent active voltage limitation semiconductor circuits may be used in
associated apparatus provided the transient conditions of the clause 7.5.1 of IEC 60079-11 standard are met.
These circuits shall also be tested in accordance with the clause 10.1.5.3 of the IEC 60079-11 standard [33].
Series current limiters
The use of three series blocking diodes in circuits of Level of Protection ‘ia’ is permitted, however, other
semiconductors and controllable semiconductor devices shall be used as series current-limiting devices only in
Level of Protection ‘ib’ or ‘ic’ apparatus. However, for power limitation purposes, Level of Protection ‘ia’
apparatus may use series current limiters consisting of controllable and non-controllable semiconductor devices.
The use of semiconductors and controllable semiconductor devices as current-limiting devices for spark ignition
limitation is not permitted for Level of Protection ‘ia’ apparatus because of their possible use in areas in which a
continuous or frequent presence of an explosive atmosphere may coincide with the possibility of a brief transient
which could cause ignition. The maximum current that may be delivered may have a brief transient but will not
be taken as Io, because the compliance with the spark ignition test of the clause 10.1 of IEC 60079-11
standard [33] would have established the successful limitation of the energy in this transient.
Protection against polarity reversal
Protection against polarity reversal shall be provided within intrinsically safe apparatus to prevent invalidation of
the type of protection as a result of reversal of the polarity of supplies to that intrinsically safe apparatus or at
connections between cells of a battery where this could occur. For this purpose, single diode shall be acceptable.
Other considerations
All the recommendations reported in the section 2.14.1 must be considered for the implementation of the VCC
supply circuit on application integrating SARA-G350 ATEX or SARA-U270 ATEX modules intended for use in
potentially explosive atmospheres. Any specific applicable requirement for the VCC supply circuit design must be
fulfilled according to all the exact applicable standards for the apparatus.
Check the detailed requisites on the pertinent normatives for the application apparatus, as for example
the IEC 60079-0 [32], IEC 60079-11 [33], IEC 60079-26 [34] standards.
2.14.3 Guidelines for antenna RF interface design
The RF output power of the SARA-G350 ATEX and SARA-U270 ATEX modules transmitter is compliant to all the
applicable 3GPP / ETSI standards, with a maximum output of 2 W RF pulse power and 1.15 mJ RF pulse energy
in 850/900 MHz bands and with a maximum output of 1 W RF pulse power and 0.58 mJ RF pulse energy in the
1800/1900 MHz bands according to the GSM/GPRS power classes stated in Table 2. The maximum average
power of SARA-U270 ATEX, according to the WCDMA power class stated in Table 3, is 250 mW.
The RF threshold power of the application device integrating a SARA-G350 ATEX or a SARA-U270 ATEX module
is defined, according to the IEC 60079-0 ATEX standard [32], as the product of the effective output power of
the module multiplied by the antenna gain (implemented/used on the application device).
The RF threshold power of the application device integrating a SARA-G350 ATEX module or a SARA-U270 ATEX
module, according to the IEC 60079-0 ATEX standard [32], must not exceed the limits shown in Table 60.
UBX-13000995 - R12 Early Production Information Design-in
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