Current sense amplifiers (also called current shunt amplifiers) are special purpose operational amplifiers (op amps) that output a voltage proportional to the current flowing in a power rail. They utilize a "sense resistor" to convert the load current in the power rail to a small voltage, which is then amplified by the current sense amplifier. Renesas offers unidirectional high-side and low-side current sense amplifiers.

What are Current Sense Amplifiers

Current sense amplifiers simplify the design of complex current monitoring circuits. The addition of a ground-sensing measurement capability enables a new level of fault detection that are useful in a wide range of power applications. Their unique features and wide range of gain and accuracy choices make them suitable for use in compact enclosures where high accuracy and low power dissipation are important.

The ISL28005 and ISL28006 are ground-sensing current sense amplifiers that amplify milli-volt current signals developed across sub-1Ω sense resistors. The simplest type of current sense amplifiers use single stage op amp circuits that take their power from the same voltage source that generates the current to be measured. These are realized using an op amp and a handful of external components to condition the amplifier to requirements of the application. As long as the measured current signal remains within the common mode voltage range of the op amp, these circuits are simple.

Example of a Current Sense Amplifier Circuit

Current Sense Amplifier circuit


Current Sense Amplifier Applications

Applications where the amplifier operates from a different power source than the load adds complexity, particularly when the measured current is at voltage levels much higher than the op amp supply voltage. In many cases an additional amplifier circuit is needed to perform the voltage translation to step-down the current sense signal to match the common mode input range of the current sense amplifier.

Current sensing in multi-output power supply systems is one application where one or more power supply output voltages must be measured using current sense amplifiers powered from a much lower supply voltage. The ISL2800x family of current sense amplifiers are ideal for these applications because they perform precise current sensing operating from supply voltages as low as 3.3V, while sensing from supply voltages as high as 28V. These current sense amplifiers are very simple, self-contained solutions requiring only an external current sense resistor. The space-saving SOT-23 package and low component count results in very small footprint.

For more design information, see AN1567: Unidirectional Current Sense Amplifiers.

Current Sense Two-Amp Topology

Current Sense Two Amp Topology

Alternatives

The ISL28006 is a high performance micropower, uni-directional high-side and low-side current sense amplifier featuring a proprietary rail-to-rail input current sensing amplifier.

The ISL28005 is a low cost micropower, uni-directional high-side and low-side current sense amplifier featuring a proprietary rail-to-rail input current sensing amplifier.

Try Renesas' family of digital power monitors, including the ISL28022 basic DPM, the ISL28023 full featured DPM and the ISL28025 DPM in a tiny package.

Renesas provides a complete portfolio for power monitor and current sensing solutions:

Op Amps provide the basic/flexible building blocks for current sensing circuits.

Current Sense Amplifiers integrate external components (i.e. gain setting resistors) to simplify design and provides analog voltage output.

Digital Power Monitors integrate ADC to provide digital output to directly interface with microcontrollers and FPGAs.

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By combining analog electronic building blocks with a 16-bit ADC, Renesas' integrated power monitors accurately measure current and voltage.
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By combining analog electronic building blocks with a 16-bit ADC, Renesas' integrated power monitors accurately measure current and voltage.
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By combining analog electronic building blocks with a 16-bit ADC, Renesas' integrated power monitors accurately measure current and voltage.

Evaluation Tools

ISL28005/6FH-xxEV1Z Current Sense Amplifier Eval Board

Evaluation Kit

ISL28005/6FH-xxEV1Z

The ISL28005/6FH-xxEV1Z contains all circuitry needed to evaluate the ISL28005 and ISL28006 in high or low-side current sense applications.