INM 5500 Rev 11
48
6.5.2 MTL5549/ MTL5549Y - Isolating Driver
Two channel, for 4/20mA HART® valve positioners with line-fault detection
The MTL5549 accepts 4/20mA floating signals from safe-area controllers to drive 2 current/
pressure converters (or any other load up to 800Ω) in a hazardous area. For HART valve
positioners, the module also permits bi-directional transmission of digital communication
signals so that the device can be interrogated either from the operator station or by a hand-held
communicator. Process controllers with a readback facility can detect open or short circuits in
the field wiring: if these occur, the current taken into the terminals drops to a preset level. The
MTL5549Y is very similar to the MTL5549 except that it provides open circuit detection only
(i.e. no short-circuit detection).
Hazardous area
Safe
are
a
Terminal Function
1 Output –ve (Ch 1)
2 Output +ve (Ch 1)
4 Output –ve (Ch 2)
5 Output +ve (Ch 2)
8 Input –ve (Ch 2)
9 Input +ve (Ch 2)
11 Input –ve (Ch 1)
12 Input +ve (Ch 1)
13 Supply –ve
14 Supply +ve
Input characteristics
Field wiring state MTL5549 MTL5549Y
Normal <6.0V <6.0V
Open-circuit <0.9mA <0.5mA
Short-circuit <0.9mA N.A.
Figure 6.26:
Top labels
for MTL5549
& MTL5549Y
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