Abstract: A clocking technique for reducing the power of PDM microphones in dual microphone systems is disclosed. A clock for a conventional PDM microphone (PDMCLK) is provided by another source. PDM microphones send serial data (PDMDAT) on the rising (“Right”) or falling (“Left”) edge of the PDMCLK clock, depending on how the microphone is configured. In a dual PDM microphone configuration, the microphones alternate sending data on the rising edges (transitions to logic-1) and falling edges (transitions to logic-0) of PDMCLK. Typically, Complementary Metal-Oxide-Semiconductor (CMOS) logic is used to transmit or drive the clock signal to the microphones. CMOS drivers consume power primarily when they transition from a logic-0 to a logic-1 or from a logic-1 to a logic-0. Thus, a free-running clock signal will produce the highest CMOS power consumption.

Abstract: An encoding technique for reducing the power of PDM microphones is disclosed. Digital MEMS microphones utilize a modulation technique called Pulse Density Modulation (PDM), where a single data line (PDMDAT) is used to convey the digital information from the microphone source to a receiver. A characteristic of PDM is that a low noise signal will produce the most transitions, a zero signal will produce an alternating bitstream of logic-1s and logic-0s, and low noise bitstreams will be rich in singleton and doubleton 1s/0s. Typically, CMOS drivers transmit the PDM bitstream signal. CMOS drivers consume power primarily when they transition, so a bitstream rich in singletons and doubletons will increase power consumption. Differential encoding with an XNOR function is used as a singleton-suppression encoder, and a differential encoding with an XOR function is used as a doubleton-suppression encoder.

Abstract: Embodiments allow for the use of the SS modulation technique (and thus for significant reduction of EMI due to clock transmission) in scenarios involving tight synchronization requirements between two devices. In particular, embodiments can be used in high-speed communication networks (e.g., high-speed Ethernet) where a clock signal embedded in the data stream at the transmitter and recovered from the data stream at the receiver is the only source for synchronization between the transmitter and the receiver (i.e., no other synchronization channel available). Embodiments are also especially useful in communication systems utilizing echo cancellers.

Abstract: Embodiments allow for the use of the SS modulation technique (and thus for significant reduction of EMI due to clock transmission) in scenarios involving tight synchronization requirements between two devices. In particular, embodiments can be used in high-speed communication networks (e.g., high-speed Ethernet) where a clock signal embedded in the data stream at the transmitter and recovered from the data stream at the receiver is the only source for synchronization between the transmitter and the receiver (i.e., no other synchronization channel available). Embodiments are also especially useful in communication systems utilizing echo cancellers.