SBOA615 November   2024 INA180 , INA180-Q1 , INA181 , INA181-Q1 , INA183 , INA185 , INA185-Q1 , INA186 , INA186-Q1 , INA190 , INA190-EP , INA190-Q1 , INA191 , INA199 , INA199-Q1 , INA209 , INA210 , INA210-Q1 , INA211 , INA211-Q1 , INA212 , INA212-Q1 , INA213 , INA213-Q1 , INA214 , INA214-Q1 , INA215 , INA215-Q1 , INA216 , INA2180 , INA2180-Q1 , INA2181 , INA2181-Q1 , INA219 , INA2191 , INA220 , INA220-Q1 , INA223 , INA225 , INA225-Q1 , INA226 , INA226-Q1 , INA228 , INA228-Q1 , INA229 , INA229-Q1 , INA2290 , INA230 , INA231 , INA232 , INA233 , INA234 , INA236 , INA237 , INA237-Q1 , INA238 , INA238-Q1 , INA239 , INA239-Q1 , INA240 , INA240-Q1 , INA241A , INA241A-Q1 , INA241B , INA241B-Q1 , INA250 , INA250-Q1 , INA253 , INA253-Q1 , INA254 , INA260 , INA280 , INA280-Q1 , INA281 , INA281-Q1 , INA290 , INA290-Q1 , INA293 , INA293-Q1 , INA296A , INA296A-Q1 , INA296B , INA296B-Q1 , INA300 , INA300-Q1 , INA301 , INA301-Q1 , INA302 , INA302-Q1 , INA303 , INA303-Q1 , INA310A , INA310A-Q1 , INA310B , INA310B-Q1 , INA3221 , INA3221-Q1 , INA381 , INA381-Q1 , INA4180 , INA4180-Q1 , INA4181 , INA4181-Q1 , INA4230 , INA4235 , INA4290 , INA700 , INA740A , INA740B , INA745A , INA745B , INA750B , INA780A , INA780B , INA790B , INA791B , LMP8278Q-Q1 , LMP8601 , LMP8601-Q1 , LMP8602 , LMP8602-Q1 , LMP8603 , LMP8603-Q1 , LMP8640 , LMP8640-Q1 , LMP8640HV

 

  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

3.2 Pulse Width Modulated Current Sensing Risks

Sensing something in-line means the shunt resistor is next to the source and subject to a switching input common-mode voltage, such as a shunt next to motor in between high and low side FETs. For in-line sensing, TI recommends to use current-sense amplifiers that have PWM Enhanced Rejection capability such as the INA240, INA241, INA253, INA254, and INA790. Functionally, other CSAs do not perform as well because of limited AC common-mode rejection, which can yield large output disturbances.

Current Sensing Risks in an H-Bridge Figure 3-2 Current Sensing Risks in an H-Bridge

Additionally, measuring in-line and even low-side of the FETs can subject the CSA to inductive kickbacks pulling input VCM below -0.3V. If using a low-side CSA (that has minimum VCM rating of GND-0.3V) on the low-side of the FET, take care to account for inductive kickbacks.

While this can seem simple to assume that the ground of the FET (PWRGND) and ground of the CSA (AGND) needs to be the same and thus VCM needs to always be 0V, this cannot be the case if there is high impedance connection between PWRGND and AGND which can create a ground loop that is exacerbated by the inductive kickback.

If significant inductive kickback voltages are measured for a low-side CSA, then the CSA can require input protection as shown in Figure 3-1 where D1 and D2 is not necessary given low voltages of inductive kickback or can be replaced with fast acting Schottky diodes for clamping.