System-Level Design of a 64-Channel Low Power Neural Spike Recording Sensor

Abstract

This paper reports an integrated 64-channel neural spike recording sensor, together with all the circuitry to process and configure the channels, process the neural data, transmit via a wireless link the information and receive the required instructions. Neural signals are acquired, filtered, digitized and compressed in the channels. Additionally, each channel implements an auto-calibration algorithm which individually configures the transfer characteristics of the recording site. The system has two transmission modes; in one case the information captured by the channels is sent as uncompressed raw data; in the other, feature vectors extracted from the detected neural spikes are released. Data streams coming from the channels are serialized by the embedded digital processor. Experimental results, including in vivo measurements, show that the power consumption of the complete system is lower than 330 μW.

An adaptive continuous‐time incremental Σ∆ ADC for neural recording implants

“…Nowadays, there is growing interest in the development of these systems especially increasing the number of recording channels. For neural recording systems with large number of channels, both low‐power consumption and small‐chip area are needed . The analog‐to‐digital converter (ADC) is one of the key components at the front‐end that its performance considerably affects the efficiency of the entire system.…”

“…In several reported systems, ADCs have 8 to 10 bit resolution, which have been designed based on the minimum required resolution for APs. The B‐noise and APs are digitized with the same resolution whereas it is not necessary that the B‐noise is to be digitized with higher resolution.…”

“…Recently, wireless neural recording implants have been widely used to observe the simultaneous activity of many neurons in the brain. 1,2 These structures have multielectrode arrays, which are inserted into the cerebral cortex to observe the electrical activity of nearby nerve cells. The electrical activity of the neurons is named as the neural spike and/or the neural action potential (AP).…”

“…For neural recording systems with large number of channels, both low-power consumption and small-chip area are needed. 2 The analog-to-digital converter (ADC) is one of the key components at the front-end that its performance considerably affects the efficiency of the entire system. Typically, successive approximation register (SAR) ADCs with 8 to 10-bit resolution and 20 kS/s sampling rate are used in the wireless neural recording systems.…”

“…13 Therefore, an ADC with high resolution (8-10 bit) is required to digitize the waveform of action potentials while an ADC with low resolution is sufficient for the B-noise. 12,13 In several reported systems, [1][2][3][4]7 ADCs have 8 to 10 bit resolution, which have been designed based on the minimum required resolution for APs. The B-noise and APs are digitized with the same resolution whereas it is not necessary that the B-noise is to be digitized with higher resolution.…”