Low Voltage Current Mode Bandgap Circuit for Accurate Reference Generation
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Solution Overview
Problem
Integrated circuits face challenges in generating accurate reference voltages at low supply voltages while minimizing power consumption and resistor area, leading to increased costs and inaccuracies in existing bandgap reference circuits.
Innovation Solution
A proportional to absolute temperature (PTAT) generator and voltage-to-current converter are used to generate zero temperature coefficient (ZTC) current and voltage, reducing the need for large resistors and improving accuracy by summing scaled voltage PTAT with fractional VBE or voltage threshold difference to achieve temperature-independent references.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large resistors are used to generate accurate reference voltages at low supply voltages, then measurement precision is improved, but area of stationary object increases
Solution Approach 1:
The patent transitions from voltage mode to current mode operation, fundamentally changing the operating parameters of the bandgap circuit. This allows the use of smaller resistors while maintaining accuracy through current-based reference generation, directly resolving the contradiction between precision and area
Solution Approach 2:
The patent replaces traditional voltage-mode bandgap circuitry with a current-mode implementation. This substitution enables accurate reference generation without requiring large resistors, as the current-mode operation inherently provides better precision at low voltages with reduced component sizes
2Measurement precision
If large resistors are used to generate accurate reference voltages, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
By changing from voltage-mode to current-mode operation, the patent eliminates the need for large, expensive resistors. The current-mode bandgap circuit achieves the same or better precision using standard-sized resistors, directly reducing manufacturing costs while maintaining accuracy
Solution Approach 2:
The patent employs standard, inexpensive resistor values that can be easily manufactured with tight tolerances, replacing the need for large-area, costly precision resistors. This makes the circuit more economical to manufacture while maintaining reference voltage accuracy
3Use of energy by stationary object
If low supply voltages are used, then power consumption is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent replaces voltage-mode operation with current-mode operation, which is inherently more suitable for low-voltage applications. The current-mode bandgap circuit maintains excellent precision even at very low supply voltages (down to 0.5V or lower), resolving the contradiction between low power consumption and measurement precision
Solution Approach 2:
By operating in current mode rather than voltage mode, the circuit achieves better precision at low supply voltages. The current-mode topology provides superior noise immunity and accuracy in the low-voltage regime, allowing the circuit to consume less power without sacrificing precision
Data Source
AI summary
A proportional to absolute temperature (PTAT) generator generates a current PTAT (IPTAT) and a fractional VBE in a first regulation loop. A level shifting voltage-to-current converter is arranged as a second regulation loop and is operable to generate a current ZTC (IZTC) and/or a voltage ZTC (VZTC). Both regulation loops are nested into each other. In an embodiment, the voltage-to-current converter is operable to sum a scaled voltage PTAT (VPTAT/Y) with the fractional VBE (VBE/X) to generate the ZTC signal. In another embodiment, the voltage-to-current converter is operable to sum a delta voltage threshold (ΔVTH) with the fractional VBE (VBE/X) to generate the ZTC signal.