SLYY234 December   2024 AMC0106M05 , AMC0106M25 , AMC0136 , AMC0311D , AMC0311S , AMC0386 , AMC0386-Q1 , AMC1100 , AMC1106M05 , AMC1200 , AMC1200-Q1 , AMC1202 , AMC1203 , AMC1204 , AMC1211-Q1 , AMC1300 , AMC1300B-Q1 , AMC1301 , AMC1301-Q1 , AMC1302-Q1 , AMC1303M2510 , AMC1304L25 , AMC1304M25 , AMC1305M25 , AMC1305M25-Q1 , AMC1306M05 , AMC1306M25 , AMC1311 , AMC1311-Q1 , AMC131M03 , AMC1336 , AMC1336-Q1 , AMC1350 , AMC1350-Q1 , AMC23C12 , AMC3301 , AMC3330 , AMC3330-Q1

 

  1.   1
  2.   Introduction
  3.   Introduction to Isolated Signal Chain
    1.     Comparing Isolated Amplifiers and Isolated Modulators
      1.      Abstract
      2.      Introduction to Isolated Amplifiers
      3.      Introduction to Isolated Modulators
      4.      Performance Comparison Between Isolated Amplifiers and Isolated Modulators
      5.      Isolated Modulators in Traction Inverters
      6.      Isolated Amplifier and Modulator Recommendations
      7.      Conclusion
    2.     TI’s First Isolated Amplifiers With Ultra-Wide Creepage and Clearance
      1.      Application Brief
  4.   Selection Trees
  5.   Current Sensing
    1.     Shunt Resistor Selection for Isolated Data Converters
      1.      17
    2.     Design considerations for isolated current sensing
      1.      19
      2.      Conclusion
      3.      References
      4.      Related Websites
    3.     Isolated Current-Sensing Circuit With ±50-mV Input and Single-Ended Output
      1.      24
    4.     Isolated Current-Sensing Circuit With ±50-mV Input and Differential Output
      1.      26
    5.     Isolated Current-Sensing Circuit With ±250-mV Input Range and Single-Ended Output Voltage
      1.      Design Goals
      2.      Design Description
      3.      Design Notes
      4.      Design Steps
      5.      Design Simulations
      6.      DC Simulation Results
      7.      Closed-Loop AC Simulation Results
      8.      Transient Simulation Results
      9.      Design References
      10.      Design Featured Isolated Amplifier
      11.      Design Alternate Isolated Amplifier
    6.     Isolated current-measurement circuit with ±250-mV input and differential output
      1.      Design Goals
      2.      Design Description
      3.      Design Notes
      4.      Design Steps
      5.      Design Simulations
      6.      DC Simulation Results
      7.      Closed Loop AC Simulation Results
      8.      Transient Simulation Results
      9.      Design References
      10.      Design Featured Op Amp
      11.      Design Alternate Op Amp
    7.     Isolated Overcurrent Protection Circuit
      1.      52
    8.     Interfacing a Differential-Output (Isolated) Amp to a Single-Ended Input ADC
      1.      54
    9.     Utilizing AMC3311 to Power AMC23C11 for Isolated Sensing and Fault Detection
      1.      Application Brief
    10.     Isolated Current-Sensing Circuit With Front-End Gain Stage
      1.      58
    11.     Accuracy Comparison of Isolated Shunt and Closed-Loop Current Sensing
      1.      60
  6.   Voltage Sensing
    1.     Maximizing Power Conversion and Motor Control Efficiency With Isolated Voltage Sensing
      1.      63
      2.      Solutions for high-voltage sensing
      3.      Integrated resistor devices
      4.      Single-ended output devices
      5.      Integrated isolated voltage-sensing use cases
      6.      Conclusion
      7.      Additional resources
    2.     Increased Accuracy and Performance with Integrated High Voltage Resistor Isolated Amplifiers and Modulators
      1.      Abstract
      2.      Introduction
      3.      High Voltage Resistor Isolated Amplifiers and Modulators Advantages
        1.       Space Savings
        2.       Improved Temperature and Lifetime Drift of Integrated HV Resistors
        3.       Accuracy Results
        4.       Fully Integrated Resistors vs. Additional External Resistor Example
        5.       Device Selection Tree and AC/DC Common Use Cases
      4.      Summary
      5.      References
    3.     Isolated Amplifiers With Differential, Single-Ended Fixed Gain and Ratiometric Outputs for Voltage Sensing Applications
      1.      Abstract
      2.      Introduction
      3.      Overview of Differential, Single-Ended Fixed Gain and Ratiometric Outputs
        1.       Isolated Amplifiers with Differential Output
        2.       Isolated Amplifiers With Single-Ended, Fixed-Gain Output
        3.       Isolated Amplifiers With Single-Ended, Ratiometric Output
      4.      Application Examples
        1.       Product Selection Tree
      5.      Summary
      6.      References
    4.     Isolated Voltage-Measurement Circuit With ±250-mV Input and Differential Output
      1.      93
    5.     Split-Tap Connection for Line-to-Line Isolated Voltage Measurement Using AMC3330
      1.      95
    6.     ±12V Voltage Sensing Circuit With an Isolated Amplifier and Pseudo-Differential Input SAR ADC
      1.      97
    7.     ±12-V voltage sensing circuit with an isolated amplifier and differential input SAR ADC
      1.      99
    8.     Isolated Undervoltage and Overvoltage Detection Circuit
      1.      101
    9.     Isolated Zero-Cross Detection Circuit
      1.      103
    10.     ±480V Isolated Voltage-Sensing Circuit With Differential Output
      1.      105
  7.   EMI Performance
    1.     Best in Class Radiated Emissions EMI Performance with Isolated Amplifiers
      1.      Best in Class Radiated Emissions EMI Performance with Isolated Amplifiers
      2.      Introduction
      3.      Current Generation of Texas Instruments Isolated Amplifiers Radiated Emissions Performance
      4.      Previous Generations of Texas Instruments Isolated Amplifiers Radiated Emissions Performance
      5.      Conclusion
      6.      References
    2.     Best Practices to Attenuate AMC3301 Family Radiated Emissions EMI
      1.      Abstract
      2.      Introduction
      3.      Effects of Input Connections on AMC3301 Family Radiated Emissions
      4.      Attenuating AMC3301 Family Radiated Emissions
        1.       Ferrite Beads and Common Mode Chokes
        2.       PCB Schematics and Layout Best Practices for AMC3301 Family
      5.      Using Multiple AMC3301 Devices
        1.       Device Orientation
        2.       PCB Layout Best Practices for Multiple AMC3301
      6.      Conclusion
      7.      AMC3301 Family Table
  8.   End Equipment
    1.     Comparing Shunt- and Hall-Based Isolated Current-Sensing Solutions in HEV/EV
      1.      128
    2.     Design Considerations for Current Sensing in DC EV Charging Applications
      1.      Abstract
      2.      Introduction
        1.       DC Charging Station for Electric Vehicles
        2.       Current-Sensing Technology Selection and Equivalent Model
          1.        Sensing of the Current With Shunt-Based Solution
          2.        Equivalent Model of the Sensing Technology
      3.      Current Sensing in AC/DC Converters
        1.       Basic Hardware and Control Description of AC/DC
          1.        AC Current Control Loops
          2.        DC Voltage Control Loop
        2.       Point A and B – AC/DC AC Phase-Current Sensing
          1.        Impact of Bandwidth
            1.         Steady State Analysis: Fundamental and Zero Crossing Currents
            2.         Transient Analysis: Step Power and Voltage Sag Response
          2.        Impact of Latency
            1.         Fault Analysis: Grid Short-Circuit
          3.        Impact of Gain Error
            1.         Power Disturbance in AC/DC Caused by Gain Error
            2.         AC/DC Response to Power Disturbance Caused by Gain Error
          4.        Impact of Offset
        3.       Point C and D – AC/DC DC Link Current Sensing
          1.        Impact of Bandwidth on Feedforward Performance
          2.        Impact of Latency on Power Switch Protection
          3.        Impact of Gain Error on Power Measurement
            1.         Transient Analysis: Feedforward in Point D
          4.        Impact of Offset
        4.       Summary of Positives and Negatives at Point A, B, C1/2 and D1/2 and Product Suggestions
      4.      Current Sensing in DC/DC Converters
        1.       Basic Operation Principle of Isolated DC/DC Converter With Phase-Shift Control
        2.       Point E, F - DC/DC Current Sensing
          1.        Impact of Bandwidth
          2.        Impact of Gain Error
          3.        Impact of Offset Error
        3.       Point G - DC/DC Tank Current Sensing
        4.       Summary of Sensing Points E, F, and G and Product Suggestions
      5.      Conclusion
      6.      References
    3.     Using isolated comparators for fault detection in electric motor drives
      1.      Introduction
      2.      Introduction to electric motor drives
      3.      Understanding fault events in electric motor drives
      4.      Achieving reliable detection and protection in electric motor drives
      5.      Use case No. 1: Bidirectional in-phase overcurrent detection
      6.      Use case No. 2: DC+ overcurrent detection
      7.      Use case No. 3: DC– overcurrent or short-circuit detection
      8.      Use case No. 4: DC-link (DC+ to DC–) overvoltage and undervoltage detection
      9.      Use case No. 5: IGBT module overtemperature detection
    4.     Discrete DESAT for Opto-Compatible Isolated Gate Driver UCC23513 in Motor Drives
      1.      Abstract
      2.      Introduction
      3.      System Challenge on Isolated Gate Drivers With Integrated DESAT
      4.      System Approach With UCC23513 and AMC23C11
        1.       System Overview and Key Specification
        2.       Schematic Design
          1.        Circuit Schematic
          2.        Configure VCE(DESAT) Threshold and DESAT Bias Current
          3.        DESAT Blanking Time
          4.        DESAT Deglitch Filter
        3.       Reference PCB Layout
      5.      Simulation and Test Results
        1.       Simulation Circuit and Results
          1.        Simulation Circuit
          2.        Simulation Results
        2.       Test Results With 3-Phase IGBT Inverter
          1.        Brake IGBT Test
          2.        Test Results on a 3-Phase Inverter With Phase to Phase Short
      6.      Summary
      7.      References
    5.     Isolated voltage sensing in AC motor drives
      1.      Introduction
      2.      Conclusion
      3.      References
    6.     Achieving High-Performance Isolated Current and Voltage Sensing in Server PSUs
      1.      Application Brief
  9.   Additional Reference Designs/Circuits
    1.     Designing a Bootstrap Charge-Pump Power Supply for an Isolated Amplifier
      1.      Abstract
      2.      Introduction
      3.      Bootstrap Power Supply Design
        1.       Selection of Charge Pump Capacitor
        2.       Simulation in TINA-TI
        3.       Hardware Test with AMC1311-Q1
      4.      Summary
      5.      Reference
    2.     Clock Edge Delay Compensation With Isolated Modulators Digital Interface to MCUs
      1.      Abstract
      2.      Introduction
      3.      Design Challenge With Digital Interface Timing Specifications
      4.      Design Approach With Clock Edge Delay Compensation
        1.       Clock Signal Compensation With Software Configurable Phase Delay
        2.       Clock Signal Compensation With Hardware Configurable Phase Delay
        3.       Clock Signal Compensation by Clock Return
        4.       Clock Signal Compensation by Clock Inversion at the MCU
      5.      Test and Validation
        1.       Test Equipment and Software
        2.       Testing of Clock Signal Compensation With Software Configurable Phase Delay
          1.        Test Setup
          2.        Test Measurement Results
        3.       Testing of Clock Signal Compensation by Clock Inversion at MCU
          1.        Test Setup
          2.        Test Measurement Results
            1.         Test Result – No Clock Inversion of Clock Input at GPIO123
            2.         Test Result – Clock Inversion of Clock Input at GPIO123
        4.       Digital Interface Timing Validation by Calculation Tool
          1.        Digital Interface With No Compensation Method
          2.        Commonly Used Method - Reduction of the Clock Frequency
          3.        Clock Edge Compensation With Software Configurable Phase Delay
      6.      Conclusion
      7.      References
    3.     Utilizing AMC3311 to Power AMC23C11 for Isolated Sensing and Fault Detection
      1.      Application Brief

ISO224 Input Voltage ISO Output, ADC Input (VOUTP - VOUTN) Digital Output ADS7945
+12V +4V 1999H
–12V –4V E666H
Power Supplies and Reference Voltages
VDD1 VDD2 and AVDD REF5050 External Ref
15V 5V 5V

Design Description

This circuit performs a ±12-V isolated voltage sensing measurement utilizing the ISO224 isolated amplifier and the ADS745 SAR ADC. The ISO224 can measure true differential signals of ±12V with a fixed gain of ⅓V/V and produces an isolated differential output voltage with an output common-mode voltage of VDD2 / 2. The ADS7945 is a fully differential input ADC with a full-scale input voltage of ±VREF and a common-mode input voltage of VREF / 2 ±200mV. Selecting a +5-V reference allows the ADS7945 to accept the full-scale and common-mode outputs from the ISO224. Capturing the ISO224 output with a fully differential input ADC doubles the system dynamic range compared to a single-ended conversion. Many high-voltage industrial applications such as Protection Relays, Channel-to-Channel Isolated ±10V Analog Input Cards, and Inverter & Motor Control. The equations and explanation of component selection in this design can be customized based on system specifications and needs.

Specifications

Specification Calculated Simulated
Transient ADC input settling at 100ksps 305µV 11µV
Conditioned signal range ±4V ±4V
Noise (at the input) 1.9mVRMS 1.73mVRMS
Closed-loop bandwidth 175kHz 185kHz

Design Notes

  1. The ADS7945 was selected due to its low power and a compatible analog input structure with the ISO224.
  2. Verify the systems linear operation for the desired input signal range. This is verified using simulation in the DC Transfer Characteristics selection.
  3. Select COG capacitors for CFILT to minimize distortion.
  4. Understanding and Calibrating the Offset and Gain for ADC Systems covers methods for error analysis. Review the link for methods to minimize gain, offset, drift, and noise errors.
  5. The TI Precision Labs - ADCs training video series covers methods for selecting the charge bucket circuit RFILT and CFILT. These component values are dependent on the amplifier bandwidth, data converter sampling rate, and data converter design. The values shown here will give good settling and AC performance for the amplifier and data converter in this example. If the design is modified, a different RC filter must be selected. Refer to Introduction to SAR ADC Front-End Component Selection for an explanation of how to select the RC filter for best settling and AC performance.

Component Selection

  1. Select an isolated amplifier based on the input voltage range and determine the output common-mode voltage and output voltage range:

    ISO224:

    • ±12-V single-ended input range
    • Fixed gain of ⅓, yielding ±4-V differential output
    • Output common-mode voltage of +2.5V
    • 4.5-V to 18-V high-side power supply, 4.5-V to 5.5-V low-side power supply
    • Input Offset: ±5mV at 25°C, ±42µV/°C maximum
    • Gain Error: ±0.3% at 25°C, ±50ppm/°C maximum
    • Nonlinearity: ±0.01% max, ±1ppm/°C
    • High-input impedance of 1.25MΩ

  2. Select an ADC with an appropriate common-mode and differential input range to pair with the +2.5-V common-mode and ±4-V differential output of the ISO224:

    ADS7945:

    • ±5-V maximum analog input range
    • Full-scale input span set by ±voltage reference
    • Input common-mode range of VREF / 2 ±0.2V
    • 2.7-V to 5.25-V power supply
    • High SNR of 84, low power of 11.6mW at 2Msps

  3. Select a voltage reference that supports the common-mode constraint set by the 2.5-V common-mode output of the ISO224 and the VREF / 2 ±0.2-V common-mode input voltage of the ADS7945. This means that the reference output voltage must be 5V, low noise, and a configurable input voltage is preferred:

    REF5050:

    • 5-V output
    • 5.2-V to 18-V input voltage power supply
    • 3μVPP/V noise

  4. Select R1FILT, R2FILT, and CFILT for settling of the input signal and sample rate of 100ksps:

    Refine the RFILT and CFILT Values is a TI Precision Labs video showing the methodology for selecting RFILT and CFILT. The final value of 120Ω and 510pF proved to settle to well below ½ of a least significant bit (LSB) within the acquisition window.

DC Transfer Characteristics

The following graph shows the simulated output for a ±15-V input. The desired linear range is a ±4-V output for a ±12-V input. This simulation shows that the linear output range is approximately ±4.6V which is well beyond the requirement.

The transfer function shows the ISO224 gain is ⅓ (that is, Gain · VIN = VOUT, (⅓)·(12V) = 4V).

AC Transfer Characteristics

The simulated bandwidth is approximately 186kHz and the gain is –9.57dB (or 0.332V/V) which closely matches the expected gain and bandwidth for the ISO224 (specified fc = 175kHz, gain = 0.333V/V).

Transient ADC Input Settling Simulation

The following simulation shows the transient settling results with an acquisition time of 9.6μs. The 11-μV settling error is well within the 0.5 × LSB limit of 305μV. See Refine the Rfilt and Cfilt Values for detailed theory on this subject.

Noise Simulation

The following noise calculation looks only at the noise of the ISO224. The ISO224 noise is substantially higher than other noise sources in the circuit, so the total noise can be approximated as the ISO224 noise. The same method can be used for the B grade.

The simulated noise is greater than the expected calculated noise. This difference is due to noise peaking in the simulation model. The noise peaking is not included in the calculation. Refer to Calculating the Total Noise for ADC Systems for detailed theory on this subject.

Design Featured Devices

Device Key Features Link Similar Devices
ISO224 ±12-V single-ended input range, Fixed gain of ⅓, yielding ±4-V differential output, output common-mode voltage of +2.5V, 4.5-V to 18-V high-side power supply, 4.5-V to 5.5-V low side power supply, input offset: ±5mV at 25°C, ±42µV/°C max, gain error: ±0.3% at 25°C, ±50ppm/°C maximum, nonlinearity: ±0.01% maximum, ±1ppm/°C, high-input impedance of 1.25MΩ www.ti.com/product/ISO224 www.ti.com/isoamps
ADS7945

±5 V max analog input range, full-scale input span set by ±voltage reference, input common mode range of VREF / 2 ±0.2V, 2.7-V to 5.25-V power supply, high SNR of 84, low power of 11.6mW at 2Msps

 www.ti.com/product/ADS7945 http://www.ti.com/opamps
REF5050 3ppm/°C drift, 0.05% initial accuracy, 4μVpp/V noise www.ti.com/product/REF5050 http://www.ti.com/vref

Design References

See Analog Engineer's Circuit Cookbooks for TI's comprehensive circuit library.

Link to Key Files

See the TINA files for Isolated Design.