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Measuring в€’48 V High-Side Current Using the AD629 Difference Amplifier, AD8603 Op Amp, AD780 Reference, and AD7453 12-Bit ADC Single-Supply Components (CN0100)
The −48 V power rail is widely used in wireless base stations and telecommunication equipment. Used in network central offices, it can vary between −48 V and −60 V. Measuring the current at that voltage typically requires components that operate on dual supplies, such as ±15 V. Typically, only the front-end conditioning amplifiers that interface directly with the −48 V rail use dual supplies. The remainder of the system operates on single supplies. However, eliminating the negative supply reduces complexity and cost. Using the AD629 and the AD8603 in this circuit allows designers to measure current at −48 V to −60 V while operating only on positive supplies.
Compared with low-side current sensing, the high-side current sensing rejects ground noise and can detect short circuits during operation.
Figure 1: Circuit Used to Measure −48 V Current (Simplified Schematic)
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