Bias Generator IR Drop Compensation for Image Sensors
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Solution Overview
Problem
Distributed power delivery networks experience non-linear IR voltage drops, leading to reduced bias control voltage and non-uniform current levels, which affects the performance of biased current mirror circuits, especially in dense circuitry with high performance requirements.
Innovation Solution
A tuned IR voltage drop network is implemented by embedding resistance networks that match the IR voltage drop profile of the power supply, using current sources on both sides of the delivery network and adjusting IR voltage drops through programmed current sources to maintain constant bias control voltage across the circuit array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the resistance of the power supply delivery network is reduced to minimize IR voltage drop, then the bias control voltage uniformity improves, but the available circuit area for power supply routing is consumed
Solution Approach 1:
The patent embeds resistance networks within the bias generator circuitry that intentionally generate IR voltage drops to counterbalance the unwanted IR voltage drops in the power supply delivery network. By converting the harmful effect of resistance into a beneficial compensating effect, the system achieves uniform bias control voltage without requiring reduced resistance or additional routing area.
2Manufacturing precision
If sampling capacitors are used to maintain static Vgs voltage, then bias control is improved, but cell size increases and noise performance deteriorates
Solution Approach 1:
The patent extracts the bias control function from the power supply delivery network and relocates it to the bias generator. By embedding resistance networks and current sources within the bias generator, the system eliminates the need for sampling capacitors distributed throughout the array, thereby reducing cell size while maintaining bias control voltage stability.
3Manufacturing precision
If sampling is performed to maintain constant Vgs, then bias uniformity improves, but coherent row-noise injection occurs
Solution Approach 1:
The patent performs preliminary bias control by embedding resistance networks that proactively compensate for IR voltage drops before they affect the bias control voltage. This preliminary action eliminates the need for subsequent sampling operations, thereby preventing coherent row-noise injection while maintaining bias uniformity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures uniform bias control voltage across the circuit array, reducing the impact of IR voltage drops and maintaining consistent performance, even in dense circuitry with high performance requirements, while allowing for adjustments in IR voltage drops based on power consumption changes.
Implementation Method 1
A bias generator is embedded with a resistance network that creates an IR voltage drop that matches an IR voltage drop profile of a power supply
Data Source
AI summary
A distributed power supply delivery network includes an analog biased circuit array having current sources for delivering current to adjacent circuits, and a resistive ladder of resistor elements, where each resistor element is disposed between adjacent current sources. A tuned IR voltage drop network is included to match voltage drops across the resistive ladder. The tuned IR voltage drop network includes series connected resistors and a static current draw to induce the IR drop. The resistors may be matched with respect to the distributed power supply delivery system. The current source providing the static current for the IR drop may be programmed based on the power supply delivery load, in order to adjust the voltage drop across the biasing delivery route and match the voltage drop in the referenced power supply.