Adaptive power regulation and data delivery for multi-module implants

Abstract

Emerging applications for implantable devices are requiring multi-unit systems with intrabody transmission of power and data through wireline interfaces. This paper proposes a novel method for power delivery within such a configuration that makes use of closed loop dynamic regulation. This is implemented for an implantable application requiring a single master and multiple identical slave devices utilising a parallel-connected 4-wire interface. The power regulation is achieved within the master unit through closed loop monitoring of the current consumption to the wired link. Simultaneous power transfer and full-duplex data communication is achieved by superimposing the power carrier and downlink data over two wires and uplink data over a second pair of wires. Measured results using a fully isolated (AC coupled) 4-wire lead, demonstrate this implementation can transmit up to 120 mW of power at 6 V (at the slave device, after eliminating any losses). The master device has a maximum efficiency of 80 % including a dominant dynamic power loss. A 6 V constant supply at the slave device is recovered 1.5 ms after a step of 22 mA.

Key Considerations for Power Management in Active Implantable Medical Devices

“…electrode) target or stimulation and/or recordingusing one or multiple implantable leads. Emerging multi-module implantable systems propose a distributed approach to the interaction with the body, and partitioning of hardware [5]. These typically have a single, centralised power source that distributes power to other modules.…”

“…2) Design Considerations: The first design consideration here is the selection of voltage range for power delivery between CI and PIs. With the designated 4-wire power delivery system [5], [10], the power consumed by the connection itself can be estimated by:…”

In-body wireline interfacing platform for multi-module implantable microsystems

“…This connects through a UART/USB interface to the IGLOO Nano FPGA development board (AGL250V2-VQG100), on which the 4WiCS digital control unit is implemented in VHDL language. A custom PCB representing the 4WiCS line interface unit includes: (i) power management; (ii) downlink line drivers; (iii) uplink line receivers; and (iv) a current sensing feedback circuit used to provide adaptive power delivery depending on the peripheral load current, as described in more detail in [3]. All active and passive components utilised in the central implant PCBs are off-theshelf components integrated within the embedded system.…”

“…This is based on one central implant CI, hub device, and multiple peripheral implants PI, distributed nodes, similarly to the BAN network architecture. In our previous work [3] [1], we coined the term multi-module approach to classify such devices. This approach allows for front-end specific functions -recording/stimulation, signal conditioning, and data conversion to be effectively performed on-site by the PIs.…”

Design Considerations for Ground Referencing in Multi - Module Neural Implants

“…Instead of the centralised approach that uses a single active implantable device, the system is now being partitioned and distributed across multiple active implantable devices each with specific functions, and located at different sites, e.g. [9], [10]. This approach addresses some of the limitations of single-module implants, however it poses a new set of challenges, mainly related to inter-module connectivity, functional reliability and patient safety.…”