Autonomous readout ASIC with 169dB input dynamic range for amperometric measurement

—A readout circuit for the measurement of amperometric sensors is presented. The circuit consists of analog frontend (AFE) and an automatic gain adjustment circuit to tune the gain of the AFE according to the input current covering a wide dynamic range of 169dB and a minimum input referred noise of 44 fA. The circuit is implemented in 0.35 µm technology, consumes 5.83 mW from 3.3 V supply voltage and occupies 0.31 mm2 silicon area

Study of electrochemical impedance of a continuous glucose monitoring sensor and its correlation with sensor performance

Abstract: In this work, we study the change in the sensitivity and the electrochemical impedance of continuous glucose monitoring sensors over time. 28-day sensitivity and EIS measurement results on four similar sensors are presented. The sensitivity of the sensor is observed to be related to its double-layer capacitance and charge-transfer resistance, based on results acquired from a sensor that showed substantial sensitivity drop. Two data clusters are extracted that relate the sensor sensitivity to its impedance before and after the sensitivity drops by more than 50%

An Integrated Platform for Differential Electrochemical and ISFET Sensing

A fully-integrated differential biosensing platform on CMOS is presented for miniaturized enzyme-based electrochemical sensing. It enables sensor background current elimination and consists of a differential sensor array and a differential readout IC (DiRIC). The sensor array includes a four-electrode sensor for amperometric electrochemical sensing, as well as a differential ISFET-based pH sensor to calibrate the biosensors. The ISFET is biased in weak inversion and co-designed with DiRIC to enable pH measurements from 1 to 14 with resolution of 0.1 pH. DiRIC enables differential current measurement in the range of ¿¿100 ¿¿A with more than 120dB dynamic range

Key Considerations for Power Management in Active Implantable Medical Devices

Within the rapidly advancing field of active implantable medical devices, power management is a major consideration. Devices that provide life critical (or avoiding life threatening) function require a dependable, always-on power source, for example pacemakers. There is then a trade-off with battery lifetime as to whether such devices employ a primary cell or rechargeable battery. With new applications requiring multi-module implants, there is now also a need for transmitting within the body from one device to another. This paper outlines the key considerations and the process to define and optimise the power management strategy. We then apply this to a case study application – developing an implanted, multi-module closed-loop neuromodulation device for the treatment of focal epilepsy

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

The recent evolution of implantable medical devicesfrom single-unit stimulators to modern implantable microsys-tems, has driven the need for distributed technologies, in whichboth the implant system and functions are partitioned across mul-tiple active devices. This multi-module approach is made possiblethanks to novel network architectures, allowing for in-body powerand data communications to be performed using implantableleads. This paper discusses the challenges in implementing suchinterfacing system and presents a platform based on one centralimplant (CI) and multiple peripheral implants (PIs) using a cus-tom 4WiCS communication protocol. This is implemented in PCBtechnology and tested to demonstrate intrabody communicationcapabilities and power transfer within the network. Measuredresults show CI-to-PI power delivery achieves 70%efficiency inexpected load condition, while establishing full-duplex data linkwith up to 4 PIs simultaneously

Adaptive Power Regulation and Data Delivery for Multi-Module Implants

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

A Configurable IC to Control, Readout and Calibrate an Array of Biosensors

We present a novel integrated circuit for a biosensing data acquisition chain. The circuit controls and reads out five bimolecular sensors as well as pH and temperature sensors for biosensor calibration. The IC supports both chronoamperometry (CA) and cyclic voltammetry (CV) measurements, which are commonly used in biosensing. Different voltage waveforms are generated to control CV by using a single configurable waveform generator and programmable constant voltage levels are produced to enable CA. To reduce the area and power consumption of the interface electronics, a unified circuit is designed for CV, CA and pH readout. The biosensors produce currents that are converted by a 13.5-bit sigma delta analog to digital converter. The circuit has been designed and realized in 0.18 μm technology. It consumes 711 μW from a 1.8 V supply voltage, making it suitable for remotely powered and implantable applications