0.48

0.44

0.40

0.36

0.32

0.28

0.24

0.20

0.16

0.12

0.08

0.04

0

0

2

4

6

8

10

12

14

16

18

20

22

V

(mV)

SENSE

24

INA271V

OUT Limit

(1)

V

CM2

V

CM1

V

CM3

V

CM4

V

,V

CM2

CM3

CM4

,andV

illustratethevariance

fromparttopartoftheV

thatcancause

CM

maximumV

withV

<20mV.

OUT

SENSE

V

limitatV

=0mV,

OUT

SENSE

0

V

£

CM1

S

£ V

NOTE:(1)INA271V

Limit=0.4V.INA270V

Limit=0.28V.

OUT

OUT

Ideal

0.40

0.36

0.32

0.28

0.24

0.20

0.16

0.12

0.08

0.04

0

0

2

4

6

8

10

12

14

16

18

V

(mV)

SENSE

20

Actual

Ideal

14

INA270, INA271

SBOS381E – FEBRUARY 2007 – REVISED JANUARY 2018

www.ti.com

Product Folder Links: INA270 INA271

Submit Documentation Feedback

Copyright © 2007–2018, Texas Instruments Incorporated

Device Functional Modes (continued)

When VSENSE approaches 0 mV, in these VCM regions, the device output accuracy degrades. A larger-than-

normal offset can appear at the current shunt monitor output with a typical maximum value of VOUT = 60 mV for

VSENSE = 0 mV. When VSENSE approaches 20 mV, VOUT returns to the expected output value with accuracy as

specified in the Electrical Characteristics. Figure 17 shows this effect using the INA271 (gain = 20).

Figure 17. Example For Low VSENSE Cases 1 and 3 (INA271, Gain = 20)

8.4.2.4 Low VSENSE Case 2: VSENSE < 20 mV, 0 V ≤ VCM ≤ VS

This region of operation is the least accurate for the INA270 family. To achieve the wide input common-mode

voltage range, these devices use two op amp front ends in parallel. One op amp front end operates in the

positive input common-mode voltage range, and the other in the negative input region. For this case, neither of

these two internal amplifiers dominates and overall loop gain is very low. Within this region, VOUT approaches

voltages close to linear operation levels for Normal Case 2.

This deviation from linear operation becomes greatest the closer VSENSE approaches 0 V. Within this region,

when VSENSE approaches 20 mV, device operation is closer to that described by Normal Case 2. Figure 18

shows this behavior for the INA271. The VOUT maximum peak for this case is determined by maintaining a

constant VS, setting VSENSE = 0 mV, and sweeping VCM from 0 V to VS. The exact VCM at which VOUT peaks

during this case varies from device to device. The maximum peak voltage for the INA270 is 0.28 V; for the

INA271, the maximum peak voltage is 0.4 V.

Figure 18. Example for Low VSENSE Case 2 (INA271, Gain = 20)