SBOSAF6 June   2024 TMCS1127

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Insulation Specifications
    6. 6.6 Electrical Characteristics
    7. 6.7 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Accuracy Parameters
      1. 7.1.1 Sensitivity Error
      2. 7.1.2 Offset Error and Offset Error Drift
      3. 7.1.3 Nonlinearity Error
      4. 7.1.4 Power Supply Rejection Ratio
      5. 7.1.5 Common-Mode Rejection Ratio
      6. 7.1.6 External Magnetic Field Errors
    2. 7.2 Transient Response Parameters
      1. 7.2.1 CMTI, Common-Mode Transient Immunity
    3. 7.3 Safe Operating Area
      1. 7.3.1 Continuous DC or Sinusoidal AC Current
      2. 7.3.2 Repetitive Pulsed Current SOA
      3. 7.3.3 Single Event Current Capability
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Current Input
      2. 8.3.2 Ambient Field Rejection
      3. 8.3.3 High-Precision Signal Chain
        1. 8.3.3.1 Temperature Stability
        2. 8.3.3.2 Lifetime and Environmental Stability
      4. 8.3.4 Internal Reference Voltage
      5. 8.3.5 Current-Sensing Measurable Ranges
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Down Behavior
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Total Error Calculation Examples
        1. 9.1.1.1 Room-Temperature Error Calculations
        2. 9.1.1.2 Full-Temperature Range Error Calculations
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Nomenclature
    2. 10.2 Device Support
      1. 10.2.1 Development Support
    3. 10.3 Documentation Support
      1. 10.3.1 Related Documentation
    4. 10.4 Receiving Notification of Documentation Updates
    5. 10.5 Support Resources
    6. 10.6 Trademarks
    7. 10.7 Electrostatic Discharge Caution
    8. 10.8 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9.1.1 Total Error Calculation Examples

Users can calculate the total error for any arbitrary device condition and current level. Consider error sources like input-referred offset current (IOS), Common Mode Rejection Ratio (CMRR), Power Supply Rejection Ratio (PSRR), sensitivity error, nonlinearity, as well as errors caused by any external magnetic fields (BEXT). Compare each of these error sources in percentage terms, as some are significant drivers of error and some have inconsequential impact to current measurement error. Offset (Equation 21), CMRR (Equation 22), PSRR (Equation 23), and external magnetic field error (Equation 24) are all referred to the input, and so are divided by the actual input current IIN to calculate percentage errors. For sensitivity error and nonlinearity error calculations, the percentage limits explicitly specified in the Electrical Characteristics table can be used.

Equation 21. e I o s = I O S I I N × 100 % = V O E S × I I N × 100 %
Equation 22. e C M R R =   C M R R × V C M I I N × 100 %
Equation 23. e P S R R ,   A =   P S R R × V S - 5 V I I N × 100 %   ;   e P S R R ,     B = e P S R R ,   C =   P S R R × V S - 3.3 V I I N × 100 %
Equation 24. e B e x t = B E X T × C M F R I I N × 100 %

where

  • VOE is the output-referred offset voltage error.
  • VCM is the input common-mode voltage.
  • ePSRR,A is the power supply rejection error for TMCS1127Axx devices.
  • ePSRR,B is the power supply rejection error for TMCS1127Bxx devices.
  • ePSRR,C is the power supply rejection error for TMCS1127Cxx devices.
  • VS is the supply voltage.
  • CMFR is the common-mode magnetic field rejection.

When calculating error contributions across temperature, only offset error and sensitivity error contributions vary significantly. To determine the offset error across temperature, use Equation 25 to calculate total input-referred offset error current, IOS, at any ambient temperature, TA.

Equation 25. e I o s , ∆ T = V O E , 25 ℃ + V O E , d r i f t × ∆ T S × I I N × 100 %

where

  • VOE,25°C is the output-referred offset error at 25°C.
  • VOE,drift is the output-referred offset drift with temperature in µV/°C.
  • ΔT is the change in temperature from 25°C.
  • S is the sensitivity of the device variant.

Sensitivity error at 25°C is specified as eS,25°C in the Electrical Characteristics table along with sensitivity variation over temperature as sensitivity thermal drift Sdrift,therm in ppm/°C. To determine the sensitivity error across temperature, use Equation 26 to calculate sensitivity error at any ambient temperature, TA, over the given application operating ambient temperature range between –40°C and 125°C.

Equation 26. e S , ∆ T = e S , 25 ℃ + S d r i f t , t h e r m × ∆ T × 100 %

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. To account for the individual error sources that are statistically uncorrelated, use a root sum square (RSS) error calculation to calculate total error. For the TMCS1127, only the input-referred offset current (IOS), CMRR, and PSRR are statistically correlated. These error terms are lumped in an RSS calculation to reflect this nature, as shown in Equation 27 for room temperature and in Equation 28 across a given temperature range. The same methodology can be applied for calculating typical total error by using the appropriate error term specification.

Equation 27. e R S S = e I o s + e P S R R + e C M R R 2 + e B e x t 2 + e S 2 + e N L 2
Equation 28. e R S S , ∆ T = e I o s , ∆ T + e P S R R + e C M R R 2 + e B e x t 2 + e S , ∆ T 2 + e N L 2

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 9-1 shows the RSS maximum total error as a function of input current for a TMCS1127A2A at room temperature and across the full temperature range with a 5.25V supply.

TMCS1127 RSS Error vs Input Current Figure 9-1 RSS Error vs Input Current