SBOSAA6A May   2024  – December 2024 INA790B

PRODUCTION DATA  

  1.   1
  2. 1Features
  3. 2Applications
  4. 3Description
  5. 4Pin Configuration and Functions
  6. 5Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Integrated Shunt Resistor
      2. 6.3.2 Safe Operating Area
      3. 6.3.3 Short-Circuit Duration
      4. 6.3.4 Temperature Drift Correction
      5. 6.3.5 Enhanced PWM Rejection Operation
    4. 6.4 Device Functional Modes
      1. 6.4.1 Adjusting the Output With the Reference Pin
        1. 6.4.1.1 Reference Pin Connections for Unidirectional Current Measurements
        2. 6.4.1.2 Ground Referenced Output
        3. 6.4.1.3 Reference Pin Connections for Bidirectional Current Measurements
        4. 6.4.1.4 Output Set to Mid-Supply Voltage
      2. 6.4.2 Adjustable Gain Set Using External Resistors
        1. 6.4.2.1 Adjustable Unity Gain
      3. 6.4.3 Thermal Alert Function
  8. 7Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Calculating Total Error
        1. 7.1.1.1 Error Sources
        2. 7.1.1.2 Reference Voltage Rejection Ratio Error
        3. 7.1.1.3 External Adjustable Gain Error
        4. 7.1.1.4 Total Error Example 1
        5. 7.1.1.5 Total Error Example 2
        6. 7.1.1.6 Total Error Example 3
        7. 7.1.1.7 Total Error Curves
      2. 7.1.2 Signal Filtering
    2. 7.2 Typical Applications
      1. 7.2.1 High-Side, High-Drive, Solenoid Current-Sense Application
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
        3. 7.2.1.3 Application Curve
      2. 7.2.2 Speaker Enhancements and Diagnostics Using Current Sense Amplifier
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
        3. 7.2.2.3 Application Curve
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9Revision History

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発注情報

7.1.2 Signal Filtering

Note that the integrated sensing element has inductance like all low-ohmic shunt resistors. Shunt inductance can lead to shunt voltage overshoots and AC gain peaking, which is undesirable if system requires linear and accurate current measurements when sensing small signal frequencies beyond 100kHz or when system can not tolerate overshoot from fast current step responses such as when comparators are tracking for fast overcurrent events. Figure 7-3 show INA790x shunt impedance vs frequency.

INA790B Shunt Impedance vs Frequency Figure 7-3 Shunt Impedance vs Frequency

Typically, inductance from low-Ohmic shunt resistors can be negated by adding a differential filter that creates a pole to flatten zero introduced from inductance. For the INA790x an internal short is provided from Kelvin sense connections to amplifier input to optimize noise, performance and quality. Thus, input resistance on these connections is very low and to apply an input filter, a capacitance between IN+ and IN- that is greater than 22µF is required. The filter capacitor must be placed as close as possible to IN+ and IN- pins. Figure 7-4 shows gain response versus frequency with and without input filter capacitor.

INA790B INA790x Gain vs Frequency Before and After Adding 22µF Input Capacitor Figure 7-4 INA790x Gain vs Frequency Before and After Adding 22µF Input Capacitor

Another option to negate the shunt inductance is to introduce the zero in transfer function at the adjustable gain-setting output buffer with a circuit configuration referred to as a RISO Dual Feedback. This operational amplifier network provides a zero to cancel out shunt inductance without sacrificing overall bandwidth nor output impedance. Figure 7-5 shows RISO Dual Feedback circuit configuration

INA790B INA790x With RISO-Dual-Feedback Figure 7-5 INA790x With RISO-Dual-Feedback

Based upon measured bandwidth and output impedance, Table 7-4 shows values for circuit components that can be used to achieve the circuit with the desired gain. Resistor tolerances under 2% is recommended. Figure 7-6 and Figure 7-7 show the load step responses with and without RISO Dual Feedback circuit with the component values in Table 7-4.

Table 7-4 INA790x RISO Dual Feedback Values
Adjustable Gain Total Gain (mV/A) RFB1 RFB2 RISO CF Min CL
1 20 19.1kΩ Open 200Ω 10nF 10nF
2 40 19.1kΩ 19.1kΩ 0Ω (Short) 0.1nF Open
3 60 19.1kΩ 9.76kΩ 0Ω (Short) 0.1nF Open
4 80 19.1kΩ 6.26kΩ 0Ω (Short) 0.1nF Open
5 100 19.1kΩ 4.7kΩ 0Ω (Short) 0.1nF Open
INA790B INA790x Load Step Responses Before and After RISO Dual Feedback for Adjustable Gain of 1
Adjustable Gain = 1, VCM = 20V, VS = 5V, VREF= 0.2V
Figure 7-6 INA790x Load Step Responses Before and After RISO Dual Feedback for Adjustable Gain of 1
INA790B INA790x Load Step Responses Before and After Feedback Capacitor For Adjustable Gain of 4
Adjustable Gain = 4, VCM = 20V, VS = 5V, VREF= 0.2V
Figure 7-7 INA790x Load Step Responses Before and After Feedback Capacitor For Adjustable Gain of 4