am452 AME, Inc., am452 Datasheet - Page 10

• Manufacturer Part Number: am452
• Description: Voltage-to-current Transducer Ic With A Differential Input - Analog Microelectronics
• Manufacturer: AME, Inc.

Figure 3: The basic difference between a 2- and 3-wire circuit
NB: The difference between GND and Ground must be clearly acknowledged!
OPERATING AM452
2- and 3-wire applications in general [2]
As AM452 can function in both 2- and 3-wire operation through external contacting, it is
important to first differentiate between the two versions of the circuit.
In 2-wire operation the IC ground is "virtual" (floating), as with a constant load resistance the
IC supply voltage V
be applied to 2-wire operation:
The reason for this is that in 2-wire operation the IC is connected in series to the actual load
resistor R
In a 2-wire system the power consumption of the overall system (AM452 plus all external
components including the signal source and adjusting resistors) may not be more than I
(e.g. 4mA).
In 3-wire operation Equation (5) no longer applies as the IC ground is connected to the
ground of the system. In 3-wire operation the supply voltage can be expressed as:
signal source and
conditioning IC
2-wire system
GND Ground
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
V
AM452 – Voltage-to-current transducer IC
CC
V
L
. This is illustrated in Figure 3.
S
GND
CC
changes according to the current. The following equation can generally
V
V
with a differential input
CC
CC
Ground
V
CC
= V
V
I
OUT
R
S
S
L
I
OUT
V
S
V
IN
R
L
signal source and
conditioning IC
3-wire system
GND Ground
V
CC
=
= V
S
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February 2008 - Rev 1.2 - Page 10/21
+49 (0)6131/91 073-30
http://www.analogmicro.de
Ground
I
OUT
=
R
GND
L
V
CC
OUTmin
=
V
(5)
(6)
S