ASIC Astable Timer Circuit for Precise Implant Clock Generation
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Solution Overview
Problem
Implantable medical devices, such as Spinal Cord Stimulation systems, face challenges with external crystal oscillators that occupy space, are prone to mechanical damage, and increase manufacturing costs, while integrated clocking circuitry struggles with temperature variability and precision frequency generation.
Innovation Solution
An improved astable timer circuit integrated into the ASIC, utilizing on-chip components and an adjustable resistor ladder with trimming bits to generate a stable clock signal with a 50% duty cycle, reduced power consumption, and insensitivity to temperature and power supply variations, allowing for precise frequency trimming and stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external crystal oscillator is used to generate a clock signal, then frequency stability and precision are improved, but device area, manufacturing cost, and reliability are worsened
Solution Approach 1:
The patent merges the clock signal generation function directly into the ASIC by integrating a ring oscillator and frequency synthesis circuitry within the same chip. This eliminates the need for external crystal oscillators and reduces device area while maintaining frequency stability through on-chip temperature compensation mechanisms.
Solution Approach 2:
The patent replaces the mechanical crystal oscillator with an electronic ring oscillator implementation. This substitution eliminates the mechanical components that occupy space and are prone to damage, while achieving comparable frequency precision through electronic feedback and temperature compensation circuits integrated on the ASIC.
2Stability of the object's composition
If an external crystal oscillator is used to generate a clock signal, then frequency stability is improved, but device complexity and manufacturing cost are worsened
Solution Approach 1:
The patent combines multiple functions including frequency generation, temperature sensing, and frequency synthesis into a single integrated circuit block within the ASIC. This reduces overall device complexity by eliminating separate external components and their associated mounting, wiring, and calibration infrastructure.
3Area of stationary object
If an on-chip RC oscillator is used to generate a clock signal, then device area is reduced, but frequency precision and temperature stability are worsened
Solution Approach 1:
The patent implements a feedback mechanism where the ring oscillator output is fed through a frequency synthesis circuit that uses phase-locked loop (PLL) technology to stabilize the frequency. Temperature sensors monitor chip temperature and adjust oscillator parameters in real-time, maintaining frequency precision despite temperature variations and achieving both compact area and high precision simultaneously.
Data Source
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AI summary
Timer circuitry completely formable in an integrated circuit (IC) for generating a clock signal in an implantable medical device is disclosed. The timer circuitry can be formed on the same Application Specific Integrated Circuit typically used in the implant, and requires no external components. The timer circuitry comprises modification to a traditional astable timer circuit. A resistance in the disclosed timer circuit can be trimmed to adjust the frequency of the clock signal produced, thus allowing that frequency to be set to a precise value during manufacturing. Precision components are not needed in the RC circuit, which instead are used to set the rough value of the frequency of the clock signal. A regulator produces a power supply for the timer circuitry from a main power supply (Vcc), producing a clock signal with a frequency that is generally independent of temperature and Vcc fluctuations.