Hall Effect against Shunt Sensing on the High Side
High-side shunts deliver superior low-current accuracy under high temperatures, while integrated Hall sensors reduce high-current thermal power loss.
High-Side Current Sensing
Upstream Monitoring
Measuring the electrical current flowing through a circuit at the positive supply rail rather than the ground return path prevents the disruption of the system ground plane. Implementing high-side current sensing involves placing a low-value shunt resistor between the power source and the load. This approach allows the system to detect short-circuits to ground occurring downstream of the sensor.
In contrast, monitoring the ground return cannot capture such faults because the short-circuit bypasses the return path entirely.
Common Mode
Measurement circuits connected to the supply rail must handle voltages that are far above the typical input range of standard operational amplifiers. For high-side current sensing, the amplifier must tolerate a high common-mode voltage while extracting a millivolt-level differential signal across the shunt resistor. Special high-voltage current-sense amplifiers are used to withstand these elevated potentials, often operating with common-mode voltages up to eighty volts or more.
These specialized components must also maintain high accuracy across a wide common-mode range to handle fluctuations in the supply voltage without introducing offset errors.
Voltage Amplification
The tiny differential voltage generated across the shunt must be scaled to match the input range of an analog-to-digital converter. During high-side current sensing, the low-offset amplifier provides a precise voltage gain that determines the overall measurement resolution. A high input impedance is necessary to prevent the amplifier from drawing current away from the sensing path.
Failure Protection
Industrial and automotive applications often subject the monitoring circuit to transient voltage spikes and reversal of the power supply. A high-side current sensing circuit must include robust transient protection to survive load dump conditions or inductive kickback. If the protective diodes or filter networks are inadequate, these overvoltage events can destroy the input stage of the sensing amplifier.
Protecting the sensing input prevents system-wide failure and ensures that current limiters can safely shut down the system during a fault.