A clock-less ultra-low power bit-serial LVDS link for Address-Event multi-chip systems

We present a power efficient clock-less fully asynchronous bit-serial Low Voltage Differential Signaling (LVDS) link with event-driven instant wake-up and self-sleep features, optimized for high speed inter-chip communication of asynchronous address-events between neuromorphic chips. The proposed LVDS link makes use of the Level-Encoded Dual-Rail (LEDR) representation and a token-ring architecture to encode and transmit data, avoiding the use of conventional large ClockData Recovery (CDR) modules with power-hungry DLL or PLL circuits. We implemented the LVDS circuits in a device fabricated with a standard 0.18μm CMOS process. The total silicon area used for such block is of 0.14mm2. We present experimental measurement results to demonstrate that, with a bit rate of 1.5Gbps and an event width of 32-bit, the proposed LVDS link can achieve transmission event rates of 35.7MEvents/second with current consumption of 19.3mA and 3.57mA for receiver and transmitter blocks, respectively. Given the clock-less and instant on/off design choices made, the power consumption of the whole link depends linearly on the data transmission rate. We show that the current consumption can go down to sub-μA for low event rates (e.g., <1kEvents/second), with a floor of 80 nA for transmitter and 42 nA for receiver, determined mainly by static off-leakage currents.