Low Side Current Sensing Amplifers

What is Low-Side Current Sensing?

Low-side current sensing connects the sensing resistor between the load and ground. Normally, the sensed voltage signal (VSEN = ISEN × RSEN) is so small that it needs to be amplified by subsequent op amp circuits (e.g., noninverting amplifier) to get the measurable Output Voltage (VOUT).

Low-Side-Current-Sensing.PNG
  • Advantages:
    • Low input Common-Mode Voltage (VCM)
    • Low VDD parts
    • Ground referenced input and output
    • Simplicity and low cost
  • Disadvantages:
    • Ground path disturbance
    • Load is lifted from system ground because the sense resistor (RSEN) adds undesirable resistance to the ground path
    • High load current caused by accidental short goes undetected

In a single-supply configuration, the most important aspect of low-side current sensing is that the VCM range of the op amp must include ground. The MCP6H0X op amp is a good choice because its VCM is from VSS – 0.3 V to VDD – 2.3 V. Considering the advantages, choose low-side current sensing where short circuit detection is not required, and ground disturbances can be tolerated.

This video discusses the use of amplifier in shunt-based current sensing applications as well as the pros and cons of high-side and low-side monitoring.

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