A 148 µW, 4-Channel Theta Phase Gamma Envelope Coupling Estimation Chip
Theta phase to gamma amplitude coupling (PAC) is involved in memory encoding and retrieval. The neural oscillations power, phase and amplitude coupling are some of the basic ingredients for memory modeling to decide on the stimulation time to enhance memory in a closed loop system. Previous work in estimating coupling was done with offline tools. Real-time energy efficient estimation is crucial to closed-loop memory stimulation, particularly health care devices for patients with neurological disorders that affect learning and memory. We present the results of the design of a real-time 4-channel chip for PAC estimation with a flexible epoch length setting in the range [0.3, 22] s. Gamma envelope, theta phase and power are also outputted in real-time with a latency of 384 ms. The 4-channel design was interleaved for area and power optimization. The chip, fabricated in a TSMC 40-nm process, consumes 148 µW, and occupies an area of 0.23 mm2.