5 Conclusion

Dynamic range is an important factor to consider when designing a current sense amplifier to a given error specification. Analysis of the amplifier is streamlined when examining the error of the total dynamic range at the maximum shunt possible, as if the design is incapable of achieving accuracy needs at this point, then no shunt choice beneath the maximum will work, regardless of power considerations, and additional steps are needed to ensure a successful design.

The topology presented in this paper is in no way exhaustive, and is only one of many different ways to expand the dynamic range of a current sensing design. In addition to MOSFETs, many additional options may be investigated, such as multiplexers, load switches, and more. However, each of these unique circuits come with potential challenges that must be taken into account to achieve this style of design, and the current range of the application is often the deciding factor.

In addition to analog output options, digital options are also a good point of investigation for such design needs. As the total system is typically integrated into these devices, including digitization of the data, they may be trimmed to where the offset voltage is optimized. The latest families of these devices, such as the INA228 and INA229, are often capable of handling up to five decades of measurement on their own, as they have 20 bits of resolution.

Finally, take care when implementing split dynamic range topologies to ensure robust performance. As the currents often being sensed in systems are direct loads, designers must ensure that the switching scheme introduced does not result in a "break before make" arrangement, where power to the load line may be lost. Also, pay attention to the burden voltage of the sense resistors for the same reasons.