am452 AME, Inc., am452 Datasheet - Page 18

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

Figure 8: OP2 as a constant current source
By solving the above system of equations and taking the given defaults for the external
components into account, the following values are computed:
R
R
R
In the 2-wire application particular attention must be paid to the overall power consumption
which may not exceed a value of 4mA across the entire temperature range.
Here it is also possible to correct the offset output current using the voltage divider at the SET stage
input.
Offset compensation using a voltage divider at SET stage
The offset value of the output current can be adjusted at the SET pin (pin 16) via voltage
divider R
too great by 0.1mA, for example (4.1mA and 20.1mA), the current must be reduced by this
amount, i.e. I
following:
Once R
SET (pin 16) is then just 257.4mV instead of 264mV and the output current has been reduced
by 0.1mA.
OP2 als Stromquelle
verschaltet
0
3
L
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
= 33
= 89.7k
= 0...900
AM452 – Voltage-to-current transducer IC
3
has been put through the equation R
3
R
S
and R
SET
2
I
AM452
V
S
BG
may only be 3.9mA. In this example and if V
4
(see Figure 7). If, due to internal offsets and parasites, the output current is
OP2
R
R
C
1
4
I
1
SET
= 74.48k
= 5k
= 2.2µF
with a differential input
1
V
2
REF
R
0
R
3
R
4
R
R
R
C
4
2
5
2
= 10k
= 39
= 100nF
= 3,9mA =
3
= 92.125k instead of 89.7k . The voltage at
Figure 9: OP2 as a voltage reference
µP
66
V
5
C VREF
V
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Fax:
Internet:
Email: [e-mail]
February 2008 - Rev 1.2 - Page 18/21
REF
R
R
R
6
7
3
5
= 5V Equation (9) yields the
k
5
OP2 als Spannungsreferenz
k
+49 (0)6131/91 073-30
http://www.analogmicro.de
2
AM452
V
BG
verschaltet
OP2
1