On-Chip Resistor Trimming via Segmented Switch Banks
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Solution Overview
Problem
Integrated resistors in integrated circuits suffer from significant resistance variance due to process variations, leading to inferior accuracy, and existing trimming circuits are inefficient in terms of area consumption and control lines.
Innovation Solution
A voltage-to-current converter with a trimmed resistor circuit that uses a combination of fixed and switched resistors, where resistors increase in resistance value by a fixed multiple, reducing the number of required resistors and control lines, allowing precise resistance adjustment with fewer switches and control lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional trimming circuits use 64 resistors with individual switches for each resistor, then precise resistance trimming is achieved, but area consumption and control line complexity increase significantly
Solution Approach 1:
The trimming circuit is segmented into two independent banks of switches (first bank and second bank) that can be selectively activated. This segmentation allows the circuit to achieve the same trimming precision with fewer simultaneously active components, reducing area consumption while maintaining precision through sequential or selective switching of the two banks.
Solution Approach 2:
The circuit dynamically selects which bank of switches to activate based on the trimming requirements. By making the switch banks selectable rather than permanently active, the circuit reduces the number of simultaneously active components, thereby reducing area consumption and control line complexity while maintaining full trimming precision when needed.
2Ease of operation
If traditional trimming circuits use 64 individual switches for 64 resistors, then precise resistance control is achieved, but the number of control lines increases
Solution Approach 1:
The control lines are segmented into two separate sets corresponding to the two banks of switches. Each bank can be controlled independently with its own control lines, reducing the total number of control lines needed compared to controlling all 64 switches simultaneously, while maintaining precise resistance control through selective activation of each bank.
Solution Approach 2:
The control line complexity is reduced by dynamically selecting which bank of switches to activate. The circuit can switch between using the first bank or second bank based on trimming needs, effectively halving the number of control lines that need to be actively managed at any given time, thereby reducing overall device complexity.
3Measurement precision
If more switches and control lines are used for trimming, then resistance precision is improved, but parasitic capacitances and settling time increase
Solution Approach 1:
By segmenting the switches into two banks, the circuit reduces the number of switches that need to settle simultaneously. When trimming is performed, only one bank needs to be active at a time, reducing the total parasitic capacitance that must charge/discharge during switching transitions, thereby reducing settling time while maintaining precision.
Solution Approach 2:
The dynamic selection between two banks of switches allows the circuit to minimize the number of active switches during any given trimming operation. This reduces the total parasitic capacitance in the active path, leading to faster settling times while maintaining the ability to achieve precise resistance values through selective switching.
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 achieves effective resistor trimming with reduced area consumption and control lines, improving accuracy and reducing settling time by minimizing parasitic capacitances and switching complexity.
Implementation Method 1
an amplifier having an inverting terminal receiving an input voltage, a non-inverting terminal coupled to a feedback node, and an output
Implementation Method 2
a first transistor having a source coupled to a supply node, a drain coupled to the feedback node, and a gate coupled to the output of the amplifier
Implementation Method 3
a trimmed resistor coupled between the feedback node and ground
Implementation Method 4
improving accuracy and reducing settling time by minimizing parasitic capacitances and switching complexity
Data Source
AI summary
An amplifier receives an input and a feedback. A first transistor controlled by the amplifier output is coupled between a supply node and the feedback. A second transistor controlled by the amplifier output is coupled to the supply node and generates a bias current. A trimmed resistor coupled between the feedback and ground includes, for trimming resolution of N-bits, where X+Y=N: M resistors, where M=2X−1, each having a resistance equal to R*(2Y)*i, i being an index having a value ranging from 1 to 2X−1, a first of the M resistors having a resistance of R*2Y, a last of the M resistors having a resistance of R*2Y*(2X−1); and M switches associated with the M resistors. Each of the M resistors is between a first node and its associated one of the M switches. Each of the M switches couples its associated one of the M resistors to a second node.