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

9.2.2 Detailed Design Procedure

The primary design parameter for using the TMCS1127 is the optimum sensitivity variant based on the required measured current levels and the selected supply voltage. Positive and negative currents are measured in this in-line phase current application example, therefore select a bidirectional variant. The TMCS1127 has a precision internal reference voltage that determines the zero current output voltage, VOUT,0A.

The internal reference voltage on TMCS1127AxA variants, with zero current output voltage VOUT,0A = 2.5V is intended for bidirectional current measurements when used with 5V power supplies. The internal reference voltage on TMCS1127BxA variants, with zero current output voltage VOUT,0A = 1.65V is intended for bidirectional current measurements when used with 3.3V power supplies. Further consideration of noise and integration with an ADC can be explored, but is beyond the scope of this application design example. The TMCS1127 output voltage VOUT is proportional to the input current IIN as defined by Equation 29 with output offset set by VOUT,0A.

Equation 29. V O U T = I I N × S + V O U T , 0 A

Design of the sensing solution focuses on maximizing the sensitivity of the device while maintaining linear measurement over the expected current input range. The TMCS1127 has a linear measurable current range that is constrained by either the positive swing to supply or negative swing to ground. To account for the operating margin, consider the previously defined minimum possible supply voltage VS,min = 4.9V. With the previous parameters, the maximum linear output voltage VOUT,max is defined by Equation 30 and the minimum linear output voltage VOUT,min is defined by Equation 31.

Equation 30. V O U T , m a x = V S , m i n - 100 m V
Equation 31. V O U T , m i n = 100 m V

Design parameters for this example application are shown in Table 9-4 along with the calculated output range.

Table 9-4 Example Application Design Parameters
DESIGN PARAMETER EXAMPLE VALUE
VOUT,max 4.8V
VOUT,0A 2.5V
VOUT,max – VOUT,0A 2.3V

These design parameters result in a maximum positive linear output voltage swing of ±2.3V about VOUT,0A = 2.5V. To determine which sensitivity variant of the TMCS1127 most fully uses this linear range, use Equation 32 to calculate the maximum current range for a bidirectional current ±IIN,max.

Equation 32. I I N ,   m a x = V O U T , m a x - V O U T , 0 A S

where

  • S is the sensitivity of the relevant AxA variant.

Table 9-5 shows the calculation for each gain variant of the TMCS1127 with the appropriate sensitivities.

Table 9-5 Maximum Full-Scale Current Ranges With 2.3V Positive Output Swing
VARIANT SENSITIVITY IIN,max
TMCS1127A1A 25mV/A ±92A
TMCS1127A2A 50mV/A ±46A
TMCS1127A3A 75mV/A ±30.6A
TMCS1127A4A 100mV/A ±23A
TMCS1127A5A 150mV/A ±15.3A
TMCS1127A6A 200mV/A ±11.5A

In general, the highest sensitivity variant is selected to provide the lowest maximum input current range that is larger than the desired full-scale current range. For the design parameters in this example, the TMCS1127A4A with sensitivity of 100mV/A is the proper selection because the maximum ±23A linear measurable range is larger than the desired ±20A full-scale current range.