INM 5500 Rev 11
47
6 .5 Analogue Output modules
The analogue output (AO) modules accept 4/20mA floating signals from safe-area controllers to
drive current/pressure converters (or any other load up to 800Ω) in a hazardous area.
6 .5 .1
MTL5546/MTL5546Y(-T) - Isolating Driver
Single channel, for 4/20mA HART® valve positioners with line-fault detection
The MTL5546 accepts a 4/20mA floating signal from a safe-area controller to drive a current/
pressure converter (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
MTL5546Y(-T) is very similar to the MTL5546 except that it provides open circuit detection
only
(i.e. no short-circuit detection).
Hazardous area
Safe area
Terminal
Function
1
Output –ve
2
ve
11
Input –ve
12
Input +ve
13
Supply –ve
14
ve
Input characteristics
Field wiring state
MTL5546
MTL5546Y
Normal
<6.0V
<6.0V
Open-circuit
<0.9mA
<0.5mA
Short-circuit
<0.9mA
N.A.
Figure 6 .25:
Top labels
for MTL5546
& MTL5546Y
