School of Electrical and Computer Engineering
Text Box: Wireless Modular Neural Microstimulating System Text Box: Three approaches were followed in design of this microsystem: (1) Interestim-1, a telemetry interface chip for operating the existing micromachined hardwired active stimulating probes by providing regulated power, serial data bit-stream, clock, and synchronization pulses. (2) Interestim-2, a modular, wireless, microstimulating chip for any kind of microelectrodes, including the passive micromachined silicon probes. (3) Interestim-3, a modular, wireless, active silicon microstimulating probe with all the wireless, stimulation, and site selection circuitry integrated on the probe backend to reduce the total number of interconnects to only two per probe. Text Box: Interestim-2B ASIC: A 4.6 mm × 4.6 mm wireless microstimulating system on a chip (SoC) with modular architecture. There are two modules on every chip, each of which can drive 32 stimulating sites. Up to 32 chips can be operated in parallel to drive a total of 2048 stimulating sites.

Interestim-2B shared the 3rd place at the 41st DAC/ISSCC student design contest in operational category.
Text Box: Related Publications: M. Ghovanloo and K. Najafi, “A wireless implantable multichannel microstimulating system-on-a-chip with modular architecture,” IEEE Trans. on Neural Sys. Rehab. Eng., vol. 15, no. 3, pp. 449-457, Sep. 2007. F.B. Myers, J.A. Simpson, and M. Ghovanloo, “A wideband wireless neural stimulation platform for high-density microelectrode arrays,” To be presented at the IEEE 28th Eng. in Med. and Biol. (EMBS-06) Conf., New York-NY, Aug. 2006 M. Ghovanloo and K. Najafi, “A modular 32-site wireless neural stimulation microsystem,” IEEE Journal on Solid-State Circuits, vol. 39, no. 12, pp. 2457-2466, Dec. 2004. K. Najafi and M. Ghovanloo, “A multichannel monolithic wireless microstimulator,” IEEE 26th EMBS Conf., pp. 4197-4200, Sep. 2004. M. Ghovanloo, K.J. Otto, D.R. Kipke, and K. Najafi, “In vitro and in vivo testing of a wireless multichannel stimulating telemetry microsystem,” IEEE 26th EMBS Conf., pp. 4294-4294, Sep. 2004. M. Ghovanloo and K. Najafi, “A modular 32-site wireless neural stimulating microsystem,” IEEE Intl. Solid-State Circuits Conf., Digest of technical papers, pp. 226-227, Feb. 2004. Text Box: Research on different blocks of this microsystem resulted in several state-of-the-art circuit designs, which can be used in similar applications such as radio-frequency identification (RFID) and smartcards. Many of these blocks are brought together in Interestim-2B, a 4.6mm×4.6mm, modular, 32-site, wireless microstimulating chip (2 modules/chip), fabricated in a 1.5-µm, 2M/2P standard-CMOS foundry process, which can receive power and stimulation data at 2.5Mbps, using a 5/10MHz FSK carrier. An on-chip full-wave rectifier, followed by a series regulator, can supply the chip with up to 50 mW. Eight current drivers per module can generate up to 65,800 stimulus pulses/sec at ±270mA full-scale, with 5 bits of resolution, ~100MΩ of output impedance, and a wide voltage compliance range that extends within 150mV and 250mV of the 5V and ground supply rails for sinking and sourcing currents, respectively. The modular architecture of Interestim-2B allows the operation of up to 64 modules in parallel, while sharing a single receiver LC-tank circuit, in order to support a total of 2048 stimulating sites. Interestim-2B was combined with 1-4, 16-site, passive, chronic, intracortical microelectrode arrays in several prototype implants, and successfully used in various in vitro and acute in vivo experiments. Text Box: Interestim-2B Implant: A 19 × 19 × 6 mm3 implantable wireless microstimulating system with 64 stimulating sites on 4 University of Michigan micromachined silicon electrode arrays. The entire implant has only 3 off-chip components. The receiver coil is mounted on the other side of the PCB. Text Box: This project seeks to develop wireless circuit interface and associated electronics for an implantable neural stimulating microsystem with a large number of stimulating sites for use in neural prostheses. The implantable microsystem should be inductively powered, button-sized, with 1024 sites, arranged in a 3-D configuration, with 128 simultaneous channels, each capable of sourcing ±100mA. The major challenges towards this goal are the implant size, microassembly method, large number of sites, effective and safe stimulation, low power consumption, and wideband wireless link between the implant and the external world.

© 2012 Maysam Ghovanloo