Bandgap Reference Circuit Integrating Precision Voltage and Current Generation
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Solution Overview
Problem
Existing reference circuits for high-speed I/O interfaces require external precision resistors to generate both precision voltage and current, leading to inefficiencies in space, cost, and increased layout area due to electrostatic discharge protection needs, while also facing stability issues with operational amplifiers and transistor operation challenges.
Innovation Solution
A reference circuit that includes a bandgap voltage reference circuit, a positive temperature coefficient calibrating circuit, a threshold voltage superposing circuit, and a precision current generator, all operating in saturation regions, to provide both precision voltage and current without external resistors, ensuring temperature independence and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external precision resistor is used to generate precision current, then precision voltage and precision current can be obtained, but layout area and cost increase
Solution Approach 1:
The invention extracts the precision current generation function from external components and integrates it into the IC circuit itself. The bandgap voltage reference circuit and operational amplifier are used to generate precision current directly within the IC, eliminating the need for external precision resistors and reducing layout area.
Solution Approach 2:
The invention merges multiple functions (voltage reference, current reference, and ESD protection) into a single integrated circuit block. The I/O pad is designed to serve both as an output terminal and as an ESD protection node, combining protective functionality with signal output without requiring separate external components.
2Measurement precision
If an I/O pad is designed in the IC circuit to generate precision current, then precision voltage and current can be obtained, but ESD protection circuit is required increasing layout area
Solution Approach 1:
The I/O pad is designed with multi-functionality, serving both as a precision voltage output terminal and as an ESD protection node. The same pad structure provides both signal output and protective functionality, eliminating the need for separate ESD protection circuits and reducing overall device complexity.
3Measurement precision
If operational amplifier is used for generating precision current, then precision current can be obtained, but stability issues arise due to phase margin
Solution Approach 1:
The operational amplifier is configured with negative feedback through the bandgap voltage reference circuit and transistor network. This feedback mechanism stabilizes the operational amplifier by controlling its phase margin, ensuring stable operation while maintaining precision current generation capability.
4Measurement precision
If external precision resistor is used, then precision current can be generated, but cost increases
Solution Approach 1:
The IC circuit generates its own precision current using internal bandgap voltage reference and operational amplifier, without requiring external precision resistors. The circuit serves itself by providing both voltage reference and current reference functions through integrated components, eliminating the need for additional external precision components and reducing overall system cost.
Data Source
AI summary
A reference circuit for providing a precision voltage and a precision current includes a bandgap voltage reference circuit, a positive temperature coefficient calibrating circuit, a threshold voltage superposing circuit and precision current generator interconnected in cascade. From the bandgap voltage reference circuit, a bandgap voltage is outputted as the precision voltage, and a PTAT current is outputted to the positive temperature coefficient calibrating circuit along with the bandgap voltage for generating a PTAT voltage. In response to the PTAT voltage from the positive temperature coefficient calibrating circuit, the threshold voltage superposing circuit generates a first voltage which is equal to the PTAT voltage plus a threshold voltage. Then the precision current generator outputs a reference current as the precision current in response to the first voltage.