SBOSA43 June   2021 TMCS1100-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Power Ratings
    6. 7.6  Insulation Specifications
    7. 7.7  Safety-Related Certifications
    8. 7.8  Safety Limiting Values
    9. 7.9  Electrical Characteristics
    10. 7.10 Typical Characteristics
      1. 7.10.1 Insulation Characteristics Curves
  8. 8 Parameter Measurement Information
    1. 8.1 Accuracy Parameters
      1. 8.1.1 Sensitivity Error
      2. 8.1.2 Offset Error and Offset Error Drift
      3. 8.1.3 Nonlinearity Error
      4. 8.1.4 Power Supply Rejection Ratio
      5. 8.1.5 Common-Mode Rejection Ratio
      6. 8.1.6 Reference Voltage Rejection Ratio
      7. 8.1.7 External Magnetic Field Errors
    2. 8.2 Transient Response Parameters
      1. 8.2.1 Slew Rate
      2. 8.2.2 Propagation Delay and Response Time
      3. 8.2.3 Current Overload Parameters
      4. 8.2.4 CMTI, Common-Mode Transient Immunity
    3. 8.3 Safe Operating Area
      1. 8.3.1 Continuous DC or Sinusoidal AC Current
      2. 8.3.2 Repetitive Pulsed Current SOA
      3. 8.3.3 Single Event Current Capability
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Current Input
      2. 9.3.2 Input Isolation
      3. 9.3.3 High-Precision Signal Chain
        1. 9.3.3.1 Temperature Stability
        2. 9.3.3.2 Lifetime and Environmental Stability
        3. 9.3.3.3 Frequency Response
        4. 9.3.3.4 Transient Response
      4. 9.3.4 External Reference Voltage Input
      5. 9.3.5 Current-Sensing Measurable Ranges
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power-Down Behavior
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Total Error Calculation Examples
        1. 10.1.1.1 Room Temperature Error Calculations
        2. 10.1.1.2 Full Temperature Range Error Calculations
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Development Support
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Support Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

10.2.2 Detailed Design Procedure

The TMCS1100-Q1 application design procedure has two key design parameters: the sensitivity version chosen (A1-A4) and the reference voltage input. Further consideration of noise and integration with an ADC can be explored, but is beyond the scope of this application design example. The TMCS1100-Q1 transfer function is effectively a transimpedance with a variable offset set by VREF, defined by Equation 28.

Equation 28. GUID-E6D05F59-BF23-4446-AFAF-301CFBB045A9-low.gif

Design of the sensing solution first focuses on maximizing the sensitivity of the device while maintaining linear measurement over the expected current input range. The linear output voltage range is constrained by the TMCS1100-Q1 linear swing to ground, SwingGND, and swing to supply, SwingVS. With the previous parameters, the maximum linear output voltage range is the range between VOUT,max and VOUT,min, as defined by Equation 29 and Equation 30.

Equation 29. GUID-FF36B31D-9607-4754-ACF8-2B7DD6C2DB98-low.gif
Equation 30. GUID-235FED8C-540E-4385-8F01-6E3F0E746393-low.gif

For a bidirectional current-sensing application, a sufficient linear output voltage range is required from VREF to both ground and the power supply. Design parameters for this example application are shown in Table 10-4 along with the calculated output range.

Table 10-4 Example Application Design Parameters
DESIGN PARAMETEREXAMPLE VALUE
SwingVS0.2 V
SwingGND0.05 V
VOUT,max4.7 V
VOUT,min0.05 V
VOUT,max - VOUT,min4.65 V

These design parameters result in a maximum linear output voltage swing of 4.65 V. To determine which sensitivity variant of the TMCS1100-Q1 most fully uses this linear range, calculate the maximum current range by Equation 31 for a unidirectional current (IU,MAX), and Equation 32 for a bidirectional current (IB,MAX).

Equation 31. GUID-4B24DE41-F016-4089-A61A-EC71EE4CE0F3-low.gif
Equation 32. GUID-ACBB8B73-B77D-4B76-859B-0787EFD8F347-low.gif

where

  • SA<x> is the sensitivity of the relevant A1-A4 variant.

Table 10-5 shows such calculation for each gain variant of the TMCS1100-Q1 with the appropriate sensitivities.

Table 10-5 Maximum Full-Scale Current Ranges With 4.65-V Output Range
SENSITIVITY VARIANTSENSITIVITYIU,MAXIB,MAX
TMCS1100A1-Q150 mV/A93 A±46.5 A
TMCS1100A2-Q1100 mV/A46.5 A±23.2A
TMCS1100A3-Q1200 mV/A23.2 A±11.6A
TMCS1100A4-Q1400 mV/A11.6 A±5.8 A

In general, select the highest sensitivity variant that provides for the desired full-scale current range. For the design parameters in this example, the TMCS1100A2-Q1 with a sensitivity of 0.1 V/A is the proper selection because the maximum-calculated ±23.2 A linear measurable range is sufficient for the desired ±20-A full-scale current.

After selecting the appropriate sensitivity variant for the application, the zero-current reference voltage defined by the VREF input pin is defined. Manipulating Equation 28 and using the linear range defined by VOUT,max, VOUT,min, and the full-scale input current, IIN,FS, calculate the maximum and minimum VREF voltages allowed to remain within the linear measurement range, shown in Equation 33 and Equation 34.

Equation 33. GUID-624189FD-FFBC-404A-A2B4-68F5964EDCDC-low.gif
Equation 34. GUID-AE9CC54C-33DB-4CD1-8376-5A84D173E8B8-low.gif

Any value of VREF can be chosen between VREF,max and VREF,min to maintain the required linear sensing range. If the allowable VREF range is not wide enough or does not include a desired VREF voltage, the analysis must be repeated with a lower sensitivity variant of the TMCS1100-Q1. Equation 28 can be manipulated to solve for the maximum allowable current in either direction by using the selected VREF voltage and the maximum linear voltage ranges as in Equation 35 and Equation 36.

Equation 35. GUID-3AF3E417-B3D0-4A03-A1ED-4BD79BD1BAAD-low.gif
Equation 36. GUID-F695A57B-0FE3-4E86-9BE4-E2B10FAF9B7E-low.gif

Table 10-6 shows the respective values for the example design parameters in Table 10-4. In this case, a VREF of 2.5 V has been selected such that the zero current output is half of the nominal power supply. This example VREF design value provides a linear input current-sensing range of –24.5 A to +22 A, with the positive current defined as current flowing into the IN+ pin.

Table 10-6 Example VREF Limits and Associated Current Ranges
REFERENCE PARAMETEREXAMPLE VALUEMAXIMUM LINEAR CURRENT SENSING RANGE
IMAX+IMAX–
VREF,min2.05 V26.5 A–20 A
VREF,max2.7 V20 A–26.5 A
Selected VREF2.5 V22 A–24.5 A

After selecting a VREF for the application design, an appropriate source must be defined. Multiple implementations are possible, but could include:

  • Resistor divider from the supply voltage
  • Resistor divider from an ADC full-scale reference
  • Dedicated or preexisting voltage reference IC
  • DAC or reference voltage from a system microcontroller

Each of these options has benefits, and the error terms, noise, simplicity, and cost of each implementation must be weighed. In the current design example, any of these options are potentially available as a 2.5-V VREF is midrail of the power supply, a common IC reference voltage, and might already be available in the system. If the primary consideration for the current application design is to maximize precision while minimizing temperature drift and noise, a dedicated voltage reference must be chosen. For this case, the LM4030C-2.5 can be chosen for to optimize system accuracy without significant cost addition. Figure 10-3 depicts the current-sense system design as discussed.

Figure 10-3 TMCS1100-Q1 Example Current-Sense System Design