Resistor-Free Low Power Voltage Reference Circuit
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Solution Overview
Problem
Conventional micro-power voltage reference circuits for wide voltage range memory applications rely on large resistors and bipolar junction transistors (BJTs), leading to mismatch issues and excessive dependence on MOSFET models, requiring significant on-chip trimming and high power consumption.
Innovation Solution
A resistor-free and amplifier-free low-power voltage reference circuit using a diode-connected transistor and a current reference circuit that generates a bias current proportional to temperature, minimizing MOSFET model dependence and reducing the number of BJTs required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large matched resistors and BJTs are used in conventional band-gap voltage reference circuits, then a stable reference voltage can be achieved, but the circuit consumes excessive power and occupies large area
Solution Approach 1:
The patent extracts and removes the large resistors and amplifier from the conventional band-gap voltage reference circuit, retaining only the essential BJT components. This extraction eliminates the major power consumption sources while preserving the core voltage reference functionality through a simplified architecture that uses minimal components to generate the PTAT voltage and compensate for temperature effects.
Solution Approach 2:
The patent applies local quality by using different operating regions for different transistors within the circuit. Specifically, some BJTs operate in the forward active region while others operate in the saturation region, allowing each component to contribute optimally to the overall temperature compensation and voltage reference stability without requiring large resistors for biasing.
2Reliability
If large matched resistors are used in conventional voltage reference circuits, then temperature compensation can be achieved, but the circuit area increases significantly
Solution Approach 1:
The patent removes the large resistors R1 and R2 from the conventional circuit architecture, replacing their temperature compensation function with a compact network of BJTs operating in different regions. This extraction achieves the same temperature stabilization effect without the area penalty of large resistor implementations.
Solution Approach 2:
The patent changes the operating parameters of the BJT components, specifically utilizing the transition between forward active and saturation regions to achieve temperature compensation. By controlling the collector-emitter voltage and current through clever circuit topology rather than large resistors, the circuit achieves temperature stability in a compact footprint.
3Reliability
If BJTs and large resistors are used in conventional circuits, then a band-gap reference voltage can be generated, but resistor mismatch and BJT mismatch degrade performance
Solution Approach 1:
The patent merges the functions of temperature compensation and voltage reference generation into a unified BJT-based network. By combining multiple BJTs in a specific configuration where their mismatch effects cancel each other out, the circuit achieves robust temperature compensation without relying on precise matching of individual components, thus improving manufacturing yield and reliability.
4Device complexity
If conventional beta multiplier voltage references using MOSFETs in sub-threshold region are used, then resistor-free operation is achieved, but excessive dependence on MOSFET models requires significant on-chip trimming
Solution Approach 1:
The patent uses BJT transistors as copies of each other in a current mirror configuration, where the fundamental BJT physics (Ebers-Moll model) provides natural temperature compensation behavior. This copying approach with BJTs eliminates the need for complex MOSFET model-based designs and reduces sensitivity to process variations, thereby minimizing trimming requirements while maintaining resistor-free operation.
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 achieves a band-gap reference voltage with minimal variation across a wide temperature range using ultra-low sub-100 nA operating current, reducing circuit area and power consumption while eliminating resistor matching issues, and is adaptable to process variations.
Implementation Method 1
a first transistor coupled with a first output of a current reference circuit. The first transistor is operable to generate a bias current that is proportional to a reference current of the current reference circuit
Implementation Method 2
a diode-connected transistor coupled with the first transistor and a second transistor coupled with said first transistor and said second transistor, wherein said reference voltage is generated at a drain of said diode-connected transistor
Implementation Method 3
One purpose of a band gap voltage reference is to balance the negative temperature coefficient of a P-N junction with the thermal voltage (VT, where VT=KT/q)
Data Source
AI summary
An embodiment of the present invention is directed to a low power voltage reference circuit. The circuit includes a first circuit for generating a PTAT voltage without using an operational amplifier. The circuit also includes a second circuit for generating the reference voltage. The first and the second circuit do not utilize a resistor.