Clock stretcher and level shifter with small component count and low power consumption

Abstract

A clock stretching circuit (,) mites between a synchronous bus (,) and a microcontroller (,) which is asleep most of the time to save electrical power. The bus is of a type in which a slow bus device can cause the sender of data to “hold” the data until the slow device is up to speed. The stretching circuit (,) is of small component count and low power consumption, and there is no requirement for a continuous clock. In one embodiment is comprised of a triple analog switch (,) and a very small number of additional components. In another embodiment a dual four-position multiplexer (,) is employed. In still another embodiment, four transistors (,) are used with handful of additional components. A level shifter (,) including an MOSFET and a large-value resistor help to minimize power drain within the bus device. The components can be external to an off-the-shelf microcontroller or can be included in an IC that also contains an embedded microcontroller.