Tutorials 1: Switching noise mitigation for integrated dc-dc converters

Mobile communication and navigation devices have fueled the demand for low power implementations to enhance battery life. A critical aspect of reducing power in these devices is the efficiency of the process of converting power from the battery to the various loads in the system. This makes high-efficiency DC-DC switching power converters a natural candidate for such task. Unfortunately, however, with the high level of integration of many noisesensitive analog/RF circuits within these devices, the ability to use and integrate these DC-DC power converters is severely limited due to the large switching noise they generate, which tends to degrade the performance of analog/RF circuits. This forces the use of alternative, inefficient, but low-noise power converters such as linear regulators, and/or large passive components for switching noise suppression. These alternative techniques reduce battery life and increase implementation cost. This tutorial will start by introducing the basic operation of DC-DC power converters and the spectral characteristics of the switching noise they generate with different types of control schemes, such as PWM, PFM, and hysteretic control schemes during DCM and CCM operation modes. This will be followed by introducing the various mechanisms by which this switching noise can couple into and degrade the performance of noise sensitive loads in large SoCs, either directly through powering of these loads, or indirectly through shared power pins and substrate. An overview of conventional switching noise mitigation techniques employed in DC-DC converters will then follow, including techniques such as post linear regulation, active ripple cancellation, multi-phase converters, delta-sigma control, and frequency hopping/stepping. Spread-spectrum and spur-free control techniques that fully eliminate spurious noise in DC-DC converters will then be presented.