High side/ Low side : current sensing

http://en.wikipedia.org/wiki/Shunt_(electrical)#Current_measurement_techniques

http://www.maxim-ic.com/app-notes/index.mvp/id/746

검색 : http://www.google.co.kr/#q=current+sensing+circuit&hl=ko&newwindow=1&prmd=ivns&ei=Hc8jTsigNIP5mAW-u42pAw&start=20&sa=N&fp=52edb59662bf9a4e&biw=870&bih=632

설명자료

 http://www.analog.com/static/imported-files/tutorials/MT-068.pdf
 http://www.powerdesignindia.co.in/STATIC/PDF/201008/PDIOL_2010AUG02_PMNG_IND_AN_01.pdf?SOURCES=DOWNLOAD

참고 : Diff OP amp : http://www.electronics-tutorials.ws/opamp/opamp_5.html

PDIOL_2010AUG02_PMNG_IND_AN_01.pdf

Traditional High-Side Monitor

Until recently, the many implementations of these two approaches were based on discrete components or semidiscrete circuitry. In their simplest form, such high-side monitors require a precision op amp and a handful of precision resistors. One common approach for high-side measurements has been the use of the classic differential amplifier, which is employed as a gain amplifier and a level shifter from the high side to ground (Figure 4). Though widely used, this discrete circuit has three major disadvantages:

• Input resistance (equal to R1) is relative low.
• Inputs usually exhibit a large difference in input resistance.
• Resistors must be very well matched to obtain an acceptable common-mode rejection ratio (CMRR): A 0.01% deviation in any resistor value lowers the CMRR to 86dB, a 0.1% deviation lowers it to 66dB, and a 1% deviation lowers it to 46dB.

High-side current monitoring, the state of the art in current measurement, is forcing the development of a number of new integrated circuits for that purpose. Low-side measuring, on the other hand, has not driven many new, interesting ICs.

 
Figure 4. The differential amplifier is a basic component in high-side current measurements.