Bandgap Reference Voltage Generator Startup Circuit
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Solution Overview
Problem
Conventional bandgap reference voltage generators face issues with slow startup at low temperatures, high complexity, high power consumption, and reliance on supply voltage, which affects stability and accuracy over PVT variations.
Innovation Solution
A bandgap reference voltage generator with a startup circuit is designed, where the startup circuit is coupled between the output and input of the bandgap reference voltage core, using a comparator to determine the need for startup and a self-biased operational amplifier to ensure a stable output, with a passive component network for stabilization and transistors to reduce current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a startup circuit is added to assist startup operations, then startup reliability is improved, but device complexity increases
Solution Approach 1:
The startup circuit is extracted as a separate, independent module from the main bandgap reference core. This allows the startup function to be implemented with minimal additional components while keeping the core reference circuit simple and unchanged during normal operation.
Solution Approach 2:
The startup circuit activates preliminary current paths through the bandgap core before the main operation begins. By establishing initial voltage and current conditions in advance, the circuit ensures reliable startup without requiring complex control logic or additional components during steady-state operation.
2Reliability
If conventional startup circuits are used, then startup assistance is provided, but power consumption increases
Solution Approach 1:
The startup circuit operates periodically rather than continuously - it activates only during the startup phase when needed, then automatically disables itself once the bandgap reference voltage reaches its operating level. This periodic operation eliminates unnecessary power consumption during normal operation while providing reliable startup assistance.
Solution Approach 2:
The startup circuit incorporates feedback mechanisms that monitor the bandgap reference voltage level and automatically control the startup circuit's activation and deactivation. This feedback control ensures the startup circuit operates only when necessary, minimizing power consumption while maintaining startup reliability.
3Ease of operation
If startup circuits are highly reliant on supply voltage VDD, then startup control is simplified, but adaptability to different supply voltages deteriorates
Solution Approach 1:
The startup circuit is designed to self-adjust and self-regulate based on the actual supply voltage conditions. By using the supply voltage itself as part of the startup mechanism rather than requiring external control signals, the circuit automatically adapts to different supply voltage levels without complex control logic or calibration.
4Reliability
If the startup circuit remains active, then startup reliability is ensured, but it undesirably affects the bandgap reference voltage generator after startup
Solution Approach 1:
The startup circuit performs its function in advance during the startup phase, establishing the necessary initial conditions for the bandgap reference core. Once startup is complete, the circuit automatically disables itself, allowing the bandgap reference to operate independently without interference. This preliminary action ensures startup reliability while eliminating negative effects during normal operation.
Data Source
AI summary
A bandgap reference voltage generator, comprises: a bias circuit configured to generate a start signal; a startup circuit having at least two serially-connected transistors configured to receive the start signal; a proportional-to-absolute-temperature (“PTAT”) generation circuit having a first current mirror, an amplifier, a resistor, and transistors; and a complementary-to-absolute-temperature (“CTAT”) generation circuit having a second current mirror, a passive network of resistors, and at least one transistor. The at least two serially-connected transistors are connected across a first input of the amplifier and a second input of the amplifier. An output of the amplifier is coupled to the first current mirror and the second current mirror. The passive network of resistors is coupled across outputs of the second current mirror. The CTAT generation circuit has an output node for outputting a bandgap reference voltage.