-

+

IN-

IN+

REF

GND

V+

OUT

:

m

10

A

5

.

2

mV

25

I

V

R

(max)

LOAD

(max)

SHUNT

(max)

SHUNT

(max)

LOAD

(max)

SHUNT

(max)

SHUNT

I

V

R

20

REF2025, REF2030, REF2033, REF2041

SBOS600C – MAY 2014 – REVISED JANUARY 2017

www.ti.com

Product Folder Links: REF2025 REF2030 REF2033 REF2041

Submit Documentation Feedback

Copyright © 2014–2017, Texas Instruments Incorporated

Typical Application (continued)

10.2.1.2.1

Shunt Resistor

is too large, issues may arise when interfacing with systems whose ground potential is actually 0 V. Also, a value

to potential interfacing issues. Therefore, limiting the voltage across the shunt resistor is important. Equation 6

(6)

Given that the maximum shunt voltage is ±25 mV and the load current range is ±2.5 A, the maximum shunt

resistance is calculated as shown in Equation 7.

(7)

To minimize errors over temperature, select a low-drift shunt resistor. To minimize offset error, select a shunt

resistor with the lowest tolerance. For this design, the Y14870R01000B9W resistor is used.

10.2.1.2.2

Differential Amplifier

The differential amplifier used for this design should have the following features:

1. Single-supply (3 V),

2. Reference voltage input,

4. Low-drift,

5. Fixed gain, and

6. Low-side sensing (input common-mode range below ground).

For this design, a current-shunt monitor (INA213) is used. The INA21x family topology is shown in Figure 51. The

INA213B specifications can be found in the INA213 product data sheet.

Figure 51. INA21x Current-Shunt Monitor Topology

The INA213B is an excellent choice for this application because all the required features are included. In general,

instrumentation amplifiers (INAs) do not have the input common-mode swing to ground that is essential for this

application. In addition, INAs require external resistors to set their gain, which is not desirable for low-drift

applications. Difference amplifiers typically have larger input bias currents, which reduce solution accuracy at

small load currents. Difference amplifiers typically have a gain of 1 V/V. When the gain is adjustable, these

amplifiers use external resistors that are not conducive to low-drift applications.