TMCS1100 datasheet(32/50 Pages) TI1

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PSRR

PSRR * (V

(%)

CMRR

CMRR * V

(%)

Input Current (A)

D007

RSS Max Error, 25°C

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TMCS1100

SBOS820A – SEPTEMBER 2019 – REVISED JUNE 2020

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Application Information (continued)

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 due to offset 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 47 illustrates the RSS maximum total error as a function of input current for a

TMCS1100A2 at room temperature and across the full temperature range with VS of 5 V.

Figure 47. RSS Error vs Input Current

10.1.1.1 Room Temperature Error Calculations

For room-temperature total-error calculations, specifications across temperature and drift are ignored. As an

example, consider a TMCS1100A1 with a supply voltage (VS) of 3.3 V, a VREF of 1.5 V, and a worst-case

common-mode excursion of 600 V to calculate operating-point-specific parameters. Consider a measurement

error due to an external magnetic field of 30 µT, roughly the Earth's magnetic field strength. The full-scale current

range of the device in specified conditions is slightly greater than 28 A; therefore, calculate error at both 25 A

and 12.5 A to highlight error dependence on the input-current level. Table 1 shows the individual error

components and RSS maximum total error calculations at room temperature under the conditions specified.

Relative to other errors, the additional error from CMRR is negligible, and can typically be ignored for total error

calculations.

Table 1. Total Error Calculation: Room Temperature Example

ERROR

COMPONENT

SYMBOL

EQUATION

% MAX TOTAL

ERROR AT IIN =

25 A

% MAX TOTAL

ERROR AT IIN =

12.5 A

Input offset error

eIos

0.24%

0.48%

CMRR error

eCMRR

0.01%

0.02%

PSRR error

ePSRR

0.27%

0.54%

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