= High-side current sensing
<High-side current sensing> measures an <electric current> with a sensor between the supply and the load, rather than between the load and its return reference as in <low-side current sensing>. With a <shunt resistor>, the useful signal is the difference between two input potentials that may both lie far above the amplifier's local reference. The <amplifier input common-mode range> therefore matters independently of the differential signal size.<LTC6115 data sheet by Analog Devices>[Page1 typical application; pp10–11, Applications Information: Current Sense]{ref}
For an illustrative12volt supply, a50milliohm <shunt resistor> carrying2amperes develops
$$
V_s=IR_s=0.100\,\mathrm V,\qquad P_s=I^2R_s=0.200\,\mathrm W.
$$
The sense terminals are at12.0 and11.9volts relative to the supply return, so their <common-mode voltage> is11.95volts. An ideal differential amplifier of gain20 would convert the100millivolt difference to2volts. A3.3volt output or digitizer range does not by itself establish that the amplifier inputs can accept11.95volts: that requires a suitable input stage and operating specifications.
The LTC6115 demonstrates an actual high-side arrangement: an external <shunt resistor> generates a differential <electric potential difference>, and external resistors set its conversion to an output signal. Its separate current-sense and voltage-sense supply conditions must not be conflated.<LTC6115 data sheet by Analog Devices>[Page1 typical application and pp2–3 electrical characteristics]{ref}
Keeping the load return connected directly to the reference avoids the reference shift introduced by a return-path <shunt resistor>. The supply-side drop still reduces the available load <electric potential difference>. Separate sense connections implement <four-terminal sensing>; measuring through shared high-current tracks instead adds their drops to the inferred <electric current>.<LTC6115 data sheet by Analog Devices>[Page11, Sense Resistor Connection, Figure3]{ref}
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