SBOA615 November   2024 INA181 , INA181-Q1 , INA186 , INA186-Q1 , INA190 , INA190-Q1 , INA240 , INA240-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2What is ESD, EOS, and Latch Up?
    1. 2.1 Electrical Overstress
    2. 2.2 Electrical Static Discharge
    3. 2.3 Latch Ups
  6. 3Risky Applications for Current Sense Amplifiers
    1. 3.1 Applications with Over Voltage Transient Surges (EOS)
    2. 3.2 Pulse Width Modulated Current Sensing Risks
    3. 3.3 Applications with Significant Electromagnetic Interference
      1. 3.3.1 Layout Best Practices for Reducing EMI Induced Latch Up or Noise
        1. 3.3.1.1 Techniques for Proper Grounding and Decoupling Capacitance
        2. 3.3.1.2 Additional and Advanced Layout Techniques
        3. 3.3.1.3 Proper Input Filtering Layout Techniques for Noise Reduction
    4. 3.4 Applications that Float the Supply (VS or GND) Pins of CSA
  7. 4Summary
  8. 5References

3.3.1.3 Proper Input Filtering Layout Techniques for Noise Reduction

  1. Input traces are considered a differential net and kept as close together as possible.
  2. Input traces go through input common-mode capacitors (CCM) and differential capacitor (CDIFF) pads.
  3. Input resistors (RFILTER) are kept under 10Ω (or 1kΩ for capacitive-coupled input CSAs such as the INA186, INA190, or INAx191). If higher input resistors are needed, then refer to this Input Resistance Error for Current Sense Amplifiers, user's guide on calculating error increase.
  4. CCM and CDIFF are placed close to the CSA input pins.
  5. CCM has a low-impedance, direct path to CSA ground pin.
  6. CDIFF is greater than 10 times the CCM value. The reason for this is to negate effects of mismatches in CCM and resulting dynamic offsets, thus keeping the sense voltage stable during sudden VCM changes.
  7. If using a capacitive-coupled CSA, the requirement is usually to add a CDIFF of > 1nF to keep input front-end capacitors stable for loads with periodic current transients or when input resistors are high or input traces are long creating high input inductance. See data sheet and this Input Resistance Error for Current Sense Amplifiers, user's guide for more information.

Figure 3-5 shows the general schematic for filtering input noise on CSAs.

Input Filtering for EMI Induced NoiseFigure 3-5 Input Filtering for EMI Induced Noise