Bandgap Reference Circuit Startup Control for Spike Mitigation
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Solution Overview
Problem
Bandgap reference circuits experience reliability issues due to start-up signals causing current spikes, which can damage connected circuits and affect voltage stability despite the need for a mechanism to prevent locking at the zero point.
Innovation Solution
A bandgap reference circuit with a control mechanism that includes a current generating circuit, a start-up circuit, an error amplifier, and a control circuit to generate a switch control signal that mitigates overshoot by delaying the trigger signal and controlling the switch circuit's activation, thereby managing the bandgap voltage and current effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a start-up circuit is added to prevent the bandgap reference circuit from locking at the zero point, then the circuit can start up normally, but a large current spike is induced which may damage connected circuits and raises reliability issues
Solution Approach 1:
The control circuit activates the start-up circuit before the main bandgap reference circuit operates, ensuring the circuit is properly initialized. The control signal enables the start-up circuit transiently to generate the necessary initial conditions, then disables it to prevent harmful current spikes during normal operation.
Solution Approach 2:
A control circuit acts as an intermediary between the start-up circuit and the rest of the bandgap reference circuit. This control circuit generates a control signal that selectively enables the start-up circuit only when needed, mediating the interaction to prevent harmful current spikes from reaching connected circuits.
2Reliability
If the start-up circuit is activated to generate a start-up signal, then the bandgap reference circuit can overcome the zero point locking issue, but voltage overshoot occurs which affects voltage stability
Solution Approach 1:
The control circuit enables the start-up circuit transiently before normal operation to establish proper initial conditions. By activating the start-up circuit only during the startup phase and then disabling it, the circuit overcomes zero point locking without causing voltage overshoot during steady-state operation.
Solution Approach 2:
The start-up circuit is activated periodically or transiently only during the startup phase through a control signal. This periodic activation ensures the circuit overcomes zero point locking initially, then remains inactive during normal operation to maintain voltage stability.
3Reliability
If a control circuit is added to mitigate overshoot by delaying the trigger signal, then voltage and current spikes are reduced, but the device complexity increases
Solution Approach 1:
A control circuit serves as an intermediary that generates a control signal to selectively enable the start-up circuit. This intermediary component coordinates the activation and deactivation timing, reducing voltage and current spikes while adding minimal complexity compared to an uncontrolled start-up circuit.
Data Source
AI summary
A bandgap reference circuit includes a current generating circuit, a switch circuit and a control circuit. The current generating circuit is triggered by a trigger signal, generated when the bandgap reference circuit starts up, to mirror a base current to generate a first current and a second current. The current generating circuit is arranged to output the first current when triggered by the triggered signal. The switch circuit is controlled by a switch control signal to be selectively coupled between the current generating circuit and a terminal coupled to a regulator. The switch circuit is arranged to, when coupled between the current generating circuit and the terminal, allow the current generating circuit to output the second current to the terminal and accordingly provide a bandgap voltage. When the first current reduces to a predetermined level, the control circuit activates generation of the switch control signal to control the switch circuit.