A mixed-signal implementation of an ADC-less ping-pong temporal front-end for sensor-to-photonic processing

Abstract

Edge sensing systems require front-end architectures that reduce data movement, latency, and energy before full downstream processing. This paper presents a mixed-signal implementation and system-level adaptation of an ADC-less ping-pong temporal sensor front-end for low-overhead frame-difference sensing. The underlying ping-pong PWM pixel principle is adopted from prior CMOS vision-sensor work; this paper does not claim the base ping-pong pixel concept itself as new. Instead, the contribution is the implementation, validation, and sensor-to-photonic interface adaptation of that temporal front-end. The adopted front-end uses odd/even phased analog state reuse and in-pixel temporal differencing to extract motion-relevant information before full-frame digitization. A PWM representation of temporal difference is digitized by a compact counter-based readout path, producing a DATA_VALID-qualified digital interface. Preliminary one-pixel mixed-signal results in a TSMC 0.18 μm environment demonstrate functionally correct operation, stable analog boundary waveforms, verified odd/even lane alternation, and repeatable interleaved 8-bit code capture. Simulation-extracted readout timing shows a 1.017 μs DATA_VALID window with zero odd/even overlap, while current architecture-level estimates indicate 70 μW to 75 μW total power and 700 fps to 1000 fps potential. The same front-end provides an electrical interface to a downstream near-sensor photonic processing stage, where temporally preprocessed outputs can be converted to optical activations rather than exporting raw image data.