INM 5500 Rev 11
44
6 .4 .3
MTL5544/MTL5544S - Repeater Power Supply
Two channel, for 4/20mA HART® for 2- or 3-wire transmitters
The MTL5544 provides fully-floating dc supplies for energising two conventional 2-wire or
3-wire 4/20mA or HART transmitters located in a hazardous area, and repeats the current in
other circuits to drive two safe-area loads. For HART transmitters, the unit allows bi-directional
transmission of digital communication signals superimposed on the 4/20mA loop current.
Alternatively, the MTL5544S acts as a current sink for a safe-area connection rather than driving
a current into the load. Separately powered current sources, such as 4-wire transmitters, can
be connected but will not support HART communication.
Hazardous area
Safe
area
Vs–
Vs+
20 to 35V dc
–
4/20mA
Load
+
–
4/20mA
Load
+
Ch 2
Ch 1
MTL5544
MTL5544S
Load
+
–
Load
+
–
4/20mA
4/20mA
Ch 2
Ch 1
Com
Tx+
Input
Com
Tx+
Input
6
5
4
3
2
1
7
8
9
10
11
12
13
14
I
I
I
I
Terminal
Function
1
Ch1 current input
2
Ch1 transmitter ve
3
Ch1 common
4
Ch2 current input
5
Ch2 transmitter ve
6
Ch2 common
7
Ch2 ve via 220Ω for HART apps.
8
Ch2 output –ve (+ve current sink)
9
Ch2 ve (–ve current sink)
10
Ch1 ve via 220Ω for HART apps.
11
Ch1 output –ve (+ve current sink)
12
Ch1 ve (–ve current sink)
13
Supply –ve
14
ve
Hazardous
area
Safe area
The MTL5544 or MTL5544S
can also be used to drive two
safe-area loads from a single
2-wire transmitter (i.e. 1 in,
2 out) by interconnecting the
input channels as shown in
the diagram (right).
Note: In this mode the HART
data is transferred via channel
1 output only.
See also the MTL5544D.
Vs–
Vs+
20 to 35V dc
–
4/20mA
Load
+
–
4/20mA
Load
+
Ch 2
Ch 1
MTL5544
MTL5544S
Load
+
–
Load
+
–
+
–
4/20mA
6
5
4
3
2
1
7
8
9
10
11
12
13
14
I
I
I
I
Figure 6 .22:
Top labels
for MTL5544
& MTL5544S
