INM 5500 Rev 11
41
6.3.4 MTL MTL5553 isolator/power supply for 31.25kbit/s fieldbuses
The MTL5553 has been specifically developed to extend 31.25kbit/s (H1) fieldbus networks into
hazardous areas. It provides power, communication and IS isolation to devices powered through
the signal conductors. The MTL5553 complies with the requirements of Fieldbus Foundation™
specified power supply Type 133 (IS power supply). To comply with fieldbus standards, each bus
must be terminated at both ends. MTL’s FBT1-IS or FCS-MBT fieldbus terminators (see section
6.33?) can be supplied for this purpose or, for installations in which the safe-area bus length
is small, the MTL5553 includes an internal safe-area terminator which is enabled by making a
link between terminals 7&8 on the top of the unit. For network and termination criteria, check
applicable fieldbus standards and specification IEC 61158-2, ISA-S50.02 for 31.25kbit/s fieldbus
systems, Foundation™ Fieldbus 31.25kbit/s Physical LayerProfile Specification FF-816 and MTL’s
Application Brief AB002.)
Hazardous area Safe area
20-35V dc
Vs-
Vs+
+ve
-ve
+ve
-ve
Host
(31.25kbit/s)
Terminator
1
2
4
5
+ve
-ve
+ve
-ve
Field
(31.25kbit/s)
6
3
2.6W Max
8
9
T
14
13
11
10
7
12
Link 7- 8 for Terminator
Terminal Function
1 Hazardous-area fieldbus device(s) connection –ve
2 Hazardous-area fieldbus device(s) connection +ve
4 Optional HHC connection –ve
5 Optional HHC connection +ve
7 Link to 8 to enable internal terminator
8 & 11 Safe-area fieldbus device(s) connection –ve
9 & 12 Safe-area fieldbus device(s) connection +ve
13 Supply –ve
14 Supply +ve
Note: To assist the process of terminating cable screens, screw terminals have
been provided in terminals 3, 6, and 10. Please note, however, that there
is no internal connection for these terminals so they are not earthed.
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