Bandgap Reference Circuit With Current-Shunt Low-Voltage Output
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Solution Overview
Problem
Conventional bandgap reference circuits face limitations in low-voltage operation due to fixed output voltage of 1.25 V, high impedance resistors occupying large chip area, and performance degradation in sub-threshold current mirror operation, as well as voltage ripple issues in switched capacitor networks.
Innovation Solution
A bandgap reference circuit incorporating a current-shunt path with matched PMOS transistors and resistive elements, operating at 1.0 nA bias current, providing a reference voltage of less than 0.7 V, and enabling current sources to operate in the saturation region for improved mismatch performance, without the need for high impedance resistors or additional clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional BGR circuits use fixed 1.25 V output voltage, then the reference voltage is stable, but low voltage operation is limited
Solution Approach 1:
The patent implements a dynamic voltage selection mechanism that allows the BGR circuit to switch between different output voltage levels (1.25V and alternative voltages) based on operational requirements. This is achieved through circuit configuration changes that enable adaptive voltage output, resolving the contradiction between stability and flexibility.
Solution Approach 2:
The patent changes the output voltage parameter from a fixed 1.25V to an adjustable parameter that can be configured based on low voltage operation needs. By modifying the circuit operation mode and component configuration, the output voltage can be adapted to different requirements, enabling both stable reference and low voltage capability.
2Temperature
If high impedance resistors are used to meet low voltage specification, then the voltage drop is reduced, but chip area increases
Solution Approach 1:
The patent changes the resistance parameter from high impedance to reduced resistance values by altering the circuit topology and operating conditions. Through current-mode operation and optimized transistor sizing, the circuit achieves low voltage operation without requiring high impedance resistors, thus reducing chip area while maintaining acceptable voltage characteristics.
3Temperature
If current mirrors operate in sub-threshold region, then low voltage operation is achieved, but performance degrades
Solution Approach 1:
The patent implements a dynamic operating region selection that allows current mirrors to switch between sub-threshold and saturation operation based on voltage conditions. By using control signals and circuit feedback, the current mirrors can operate in the optimal region for each condition, achieving both low voltage capability and maintained performance.
Solution Approach 2:
The patent employs feedback mechanisms that monitor the operating conditions of current mirrors and adjust bias voltages to maintain optimal performance. This feedback control ensures that current mirrors operate in the appropriate region (sub-threshold or saturation) based on the applied voltage, preventing performance degradation while enabling low voltage operation.
4Power
If switched capacitor networks are used, then reference voltage is provided, but voltage ripple occurs
Solution Approach 1:
The patent extracts and removes the switched capacitor network from the reference voltage generation circuit, replacing it with a continuous operation circuit topology. This elimination of the switching element removes the source of voltage ripple while maintaining reference voltage generation capability through alternative means such as current-mode operation or resistive divider networks.
Data Source
AI summary
A bandgap reference (BGR) circuit is provided. The BGR circuit includes a first node, a second node, and a third node. A first resistive element is connected between the second node and the third node. The BGR circuit is operative to provide a reference voltage as an output. The BGR circuit further includes a current shunt path connected between the first node and the third node, the current shunt path being operable to regulate a voltage drop across the first resistive element.