Reference Current Circuit Area Reduction via Parallel Branch Segmentation
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Solution Overview
Problem
Conventional reference current circuits require a significant amount of resistance, making it difficult to reduce the area of semiconductor integrated circuits due to the large total resistance necessary for the BGR type reference current circuit.
Innovation Solution
A reference current circuit design that includes a current mirror circuit, diodes, and resistors, where the current distribution and transistor configurations are optimized to maintain a predetermined current ratio and control temperature-dependent potential differences, allowing for reduced resistance and area occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional BGR type reference current circuit is used to achieve temperature stability and power supply independence, then the reference current characteristics are improved, but the total resistance required increases significantly
Solution Approach 1:
The patent divides the reference current circuit into multiple parallel branches, each containing diodes and transistors configured to generate portioned reference currents. By segmenting the circuit functionality across multiple paths, the total resistance requirement is reduced while maintaining the temperature compensation mechanism that ensures stability.
Solution Approach 2:
The patent combines multiple reference current paths into a unified output structure where currents from different branches are merged. This merging approach allows the circuit to achieve the required temperature stability and power supply independence with lower individual branch resistances, thereby reducing the total resistance and circuit area.
2Reliability
If a conventional BGR type reference current circuit is used to achieve temperature stability, then the reference current characteristics are improved, but the resistance occupancy area increases
Solution Approach 1:
The patent segments the resistance requirements into multiple smaller resistance elements distributed across parallel branches. Each branch contains diodes and transistors that contribute to the overall temperature compensation, allowing the use of smaller resistance values that occupy less area while collectively achieving the required temperature stability.
Solution Approach 2:
The patent transitions from a single-series resistance path to a multi-parallel branch structure, effectively adding a dimensional aspect to the circuit topology. This dimensional change allows current to flow through multiple paths simultaneously, reducing the equivalent resistance and the physical area required for resistance elements.
3Area of stationary object
If the resistance is reduced to minimize circuit area, then the area occupancy is improved, but the temperature stability may be compromised
Solution Approach 1:
The patent assigns different functional qualities to different parts of the circuit. Each branch contains diodes and transistors with specific characteristics tailored to that branch's role in the overall temperature compensation mechanism. This local optimization ensures that even with reduced resistance values, each segment contributes appropriately to maintaining temperature stability.
Solution Approach 2:
The patent incorporates feedback mechanisms where the output currents from multiple branches are combined and regulated to maintain stable reference current characteristics. The feedback control ensures that temperature variations are compensated for, maintaining reliability even when individual branch resistances are reduced to minimize area.
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
The solution effectively reduces the necessary resistance in the BGR type reference current circuit, thereby minimizing the area of semiconductor integrated circuits while maintaining temperature stability and independence from power supply voltage variations.
Implementation Method 1
the relationship between the current I1 flowing in the diode D1 and the anode potential V1 is expressed by Expression 23. Further, the current I3 is m times the current I1, as described above, and accordingly, the relationship between the current I3 (=m·I1) and the anode potential Vd of the diode D2 is expressed by Expression 24
Data Source
AI summary
A current mirror circuit 10 is formed to have a current ratio (a transistor size ratio) of 1:m. As well, respective pairs of nMOS transistors MN1, MN3 and nMOS transistors MN2, MN4 are formed to have a current ratio of 1:m. Two currents output from the current mirror circuit 10 are each distributed to two. The distributed currents flowing in the nMOS transistors MN2, MN4 are added and are then allowed to flow into one resistor R2. Hence, for the resistor R2, only one resistor in which current of double flows suffices when m=1, for example. This effortlessly reduces the necessary resistance to one fourth.