Input Current (A)

0

5

10

15

20

25

0

1

2

3

4

5

6

7

8

9

10

D007

RSS Error, 25°C

566 (UURU ±

ƒ& WR

ƒ&

OS, T

REF

EXT

2

2

2

2

2

RSS, T

I

PSRR

CMRR

V

B

S, T

NL

e

(%)

e

e

e

e

e

e

e

'

'

'

OS

REF

EXT

2

2

2

2

2

RSS

I

PSRR

CMRR

V

B

S

NL

e

(%)

e

e

e

e

e

e

e

19

TMCS1100

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SBOS820 – SEPTEMBER 2019

Product Folder Links: TMCS1100

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Copyright © 2019, Texas Instruments Incorporated

Application Information (continued)

Because the statistical probability of any device actually existing in this worst case corner is insignificant, a better

methodology is to use a root sum squared (RSS) calculation for uncorrelated error sources. This method takes

into account the statistically uncorrelated nature of the individual error terms to provide a more realistic total error

based on the distributions of each error component. For the TMCS1100, only the input referred offset current

to reflect this nature, as shown in Equation 24 for room temperature and Equation 25 for across a given

temperature range.

(24)

(25)

The total error calculation has a strong dependence on the actual input current; therefore, always calculate total

error across the dynamic range that is required. These curves asymptotically approach the sensitivity and

nonlinearity error at high current levels, and approach infinity at low current levels because of error terms with

input current in the denominator. Key figures of merit for any current-measurement system include the total error

percentage at full-scale current, as well as the dynamic range of input current over which the error remains below

some key level. Figure 9 illustrates the total RSS error as a function of input current for a TMCS1100A2 at room

Figure 9. RSS Error vs Input Current