INA821 datasheet(29/50 Pages) TI2

29 / 50 page

= V

G + V

OUT V

REF

R + R

= V

G + V

= (I

R )

G + V

OUT I

REF

RG = 10.4 NŸ

R3 =

20 Ÿ

R2 = 4.17 NŸ

R1 = 100 NŸ

INA821

VOUT

±10 V

±20 mA

2.5 V ± 2.3 V

+VS

-VS

REF

15 V

REF5025

1 F

VOUT

VIN

GND

1 F

15 V

-15 V

-IN

+IN

OUT

INA821

www.ti.com

SBOS893D – AUGUST 2018 – REVISED JUNE 2020

Product Folder Links: INA821

Submit Documentation Feedback

9.2 Typical Application

Figure 69 shows a three-pin programmable-logic controller (PLC) design for the INA821. This PLC reference

design accepts inputs of ±10 V or ±20 mA. The output is a single-ended voltage of 2.5 V ±2.3 V (or 200 mV to

4.8 V). Typically, PLCs have these input and output ranges.

Figure 69. PLC Input (±10 V, 4 mA to 20 mA)

9.2.1 Design Requirements

For this application, the design requirements are as follows:

•

4-mA to 20-mA input with less than 20-

Ω burden

•

±20-mA input with less than 20-

Ω burden

•

±10-V input with impedance of approximately 100 k

Ω

•

Maximum 4-mA to 20-mA or ±20 mA burden voltage equal to ±0.4 V

•

Output range within 0 V to 5 V

9.2.2 Detailed Design Procedure

There are two modes of operation for the circuit shown in Figure 69: current input and voltage input. This design

requires R1 >> R2 >> R3. Given this relationship, Equation 3 calculates the current input mode transfer function.

where

•

G represents the gain of the instrumentation amplifier.

•

VD represents the differential voltage at the INA821 inputs.

•

VREF is the voltage at the INA821 REF pin.

•

IIN is the input current.

(3)

Equation 4 shows the transfer function for the voltage input mode.

where

•

VIN is the input voltage

(4)

INA821 Datasheet(PDF) 29 Page - Texas Instruments

INA821 Datasheet(HTML) 29 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

Datasheet Download

Link URL