Sensing and controlling supply current flow are a fundamental re-
quire ment in most all electronic systems from battery-operated,
portable equipment to mobile or fixed-platform power manage-
ment and dc motor control. High-side current-sense amplifiers (or
“CSAs”) are useful in these applications especially where power
consumption is an important design parameter. New CSA devel-
opments offer even greater benefits in allowing engineers to save
power without sacrificing performance.
With the right combination of small form factor, low supply-current operation, wide op–
erating supply-voltage range, low input offset voltage (VOS) and gain errors, and fixed
gain options, design engineers now have even more options for high-side current-sens-
ing amplification. As a result, new CSA enhancements enable the next generation of
battery-powered, hand-held portable instruments addressing power management, mo-
tor control, and fixed-platform applications.
1. Unidirectional Current Sense Amplifiers
The internal configuration of some unidirectional CSAs is based on a commonly-used operational amplifier (op amp) circuit for measur-
ing load currents in the presence of high-common-mode voltages. In the general case, a CSA monitors the voltage across an external
sense and generates an output voltage as a function of load current. Referring to the typical application circuit shown in the figure be-
low, featuring the TS1100, the inputs of the op-amp-based circuit are connected across an external RSENSE. At the RS- terminal, the
applied voltage is ILOAD x RSENSE.
Figure 1.1. Typical Application for a High-Precision Unidirectional Current-Sense Amplifier (TS1100)
Since the RS- terminal is the non-inverting input of the internal op amp, op-amp feedback action forces the inverting input of the internal