am452 AME, Inc., am452 Datasheet - Page 14

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

9. For applications where I
10. If signal source and/or input amplifier IA have a negative offset this can be compensated
DIMENSIONING
Two possible dimensioning methods are suggested here.
Dimensioning the external components according to the equations given in the data
sheet
Dimensioning according to the equations given in the data sheet enables all modules to be
used, making it possible for the setup to be adapted to suit the most diverse application
requirements.
As a rule the offset of the AM452 input signal must be taken into account. If an input signal
offset is present and an offset current of I
condition then applies:
V
negative offset, the offset can be set via pin 13 (ZA) and voltage divider R
2). Equation (1) forms the basis for all other equations in this particular case.
If the offset is negligible, Equations (9) and (10) apply. See the following applications for
further details.
Dimensioning AM452's external components using an Excel spreadsheet
AM452's external components can also be dimensioned with the help of Excel spreadsheet
Kali_AM452.xls when the input signal is positive (see [3]). The algorithm is such that the
offset output current of 4mA can only be set via pin 13 (ZA) of the zero adjust stage. The SET
stage is not active. The full-scale output current is set to 20mA using the OP1 gain setting.
The calibration process is also based on the condition that the output signal should be a
4...20mA current loop signal in 2-wire operation.
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
OS.IA
following condition applies to the IA input values:
for using corrective voltage V
positive offset at the input IA.
AM452 – Voltage-to-current transducer IC
the positive offset at the input IA (see: chapter before). Should the signal source have a
V
V
V
V
with a differential input
OS
OS
FS
FS
.
.
.
.
IA
IA
IA
IA
OUT min
I
I
I
I
OUT
OUT
OUT
OUT
ZA
max
max
min
min
> 0mA (e.g.
and a suitable voltage divider (R
, where V
, where V
OUT min
FS.IA
4mA) in both 2- and 3-wire applications the
FS.IA
> 0mA
is the maximum input signal and V
is the maximum input signal and
is required, the following boundary
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6
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and R
6
and R
7
; see Figure 2).
7
(see Figure
OS.IA
the