Monolithic current-sensing topology for system-on-chip applications

Abstract

A passive current-sensing architecture operating based on electromotive force phenomena is presented. The proposed architecture is capable of sensing a varying current over a wide range of frequencies.Simulation and measurement results of a proof-of-concept prototype implemented in a 0.13 mm CMOS confirm the performance of the presented technique for currents with frequencies up to 8 GHz. In the presented experimental results, the high-frequency performance limit is due to the measurement setup. Furthermore, the method can be used to sense currents over a wide range of amplitudes and the amplitude detection sensitivity of the technique improves as the frequency of the current signal being measured increases.Introduction: Sensing current has a wide range of applications in many integrated circuit (IC) and system-on-chip (SoC) designs. The applications of current sensing extend from fault diagnosing in complex ICs [1, 2] to monitoring current in switching DC -DC converters [3,4], to protecting confidentiality of cryptosystems [5], to testing and analysing the performance of mixed-signal and RF circuits [2]. In many such applications it is desirable to use a non-invasive current-sensing technique, i.e. the sensing circuit virtually does not disturb the test circuit current. In particular, many present and emerging applications require a high-bandwidth current sensing circuit. State-of-the-art monolithic current-sensing schemes have bandwidths in the range of a few megahertz up to 3.4 GHz [1 -5]. Although a current-sensing technique that uses exotic material and is based on giant magneto impedance (GMI) effect with bandwidths up to 30 GHz has been previously discussed (refer to [6] for an overview of this and other techniques), such techniques require a relatively large footprint as well as use of exotic materials and are not amenable to implementation in standard CMOS processes. Given that emerging applications are operating at increasingly higher frequencies, having an efficient high-bandwidth current-sensing technique suitable for integration in low-cost CMOS technologies is desirable. In this Letter, a simple electromotive-force-based technique that operates over a wide frequency range and requires a small footprint for non-invasive current-sensing in CMOS ICs and SoCs is presented.