OS

EXT

2

2

2

2

RSS

I

PSRR

CMRR

B

S

NL

e

(%)

e

e

e

e

e

e

OS, T

EXT

worst, T

I

PSRR

CMRR

B

S, T

NL

e

(%)

e

e

e

e

e

e

'

'

'

OS

EXT

worst

I

PSRR

CMRR

B

S

NL

e

(%)

e

e

e

e

e

e

T

S

S

S,drift

S,FT

e

(%)

min e

e

* 1000 * T;e

'

ª

º

'

¬

¼

OS, T

OS,RT

OS,drift

OS,FT

I

IN

min I

I

* T;I

e

(%)

I

'

ª

º

'

¬

¼

EXT

EXT

B

IN

B

G

e

(%)

I

S

PSRR

IN

PSRR * (V

5)

e

(%)

I

CM

CMRR

IN

CMRR * V

e

(%)

I

OS

OS

I

IN

I

e

(%)

I

19

TMCS1101

www.ti.com

SBOS825 – SEPTEMBER 2019

Product Folder Links: TMCS1101

Submit Documentation Feedback

Copyright © 2019, Texas Instruments Incorporated

Application Information (continued)

10.1.1 Total Error Calculation Examples

Total error can be calculated for any arbitrary device condition and current level. Error sources considered should

include input-referred offset current, power-supply rejection, input common-mode rejection, sensitivity error,

nonlinearity, and the error caused by any external fields. Compare each of these error sources in percentage

terms, as some are significant drivers of error and some have inconsequential impact to current error. Offset

(Equation 18), CMRR (Equation 19), PSRR (Equation 20), and external field error (Equation 21) are all referred

sensitivity error and nonlinearity error, the percentage limits explicitly specified in the Electrical Characteristics

table can be used.

(18)

(19)

(20)

(21)

When calculating error contributions across temperature, only the input offset current and sensitivity error

contributions vary significantly. In both cases, specifications for both the maximum device temperature range and

the parameter drift across temperature are provided. For determining actual performance limits across a

narrower temperature range than the specified –40°C to +125°C, use Equation 22 and Equation 23 for offset

error and sensitivity error, respectively. In both of these calculations, the maximum specified drift for the

parameter can be multiplied by the desired temperature deviation from room temperature (ΔT). Use the smaller

is specified in ppm/°C, and must be converted to percentage error.

(22)

(23)

In order to accurately calculate the total expected error of the device, the contributions from each of the individual

components above must be understood in reference to operating conditions. There are two separate ways to

calculate total error for any particular system. In a worst case scenario, each error term would be at its absolute

maximum with the same polarity. In such a case, the total system error would be a mathematical summation of

each individual error source, as shown in Equation 24 for room temperature. For across temperature worst case

error, the input referred offset and sensitivity error for the relevant range should be substituted in place of the

room temperature values, as in Equation 25.

(24)

(25)

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 TMCS1101, only the input referred offset current

to reflect this nature, as shown in Equation 26 for room temperature and Equation 27 for across a given

temperature range.

(26)