Glitch-Immune Intermediate Supply Circuit With Reverse Current Blocking
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Solution Overview
Problem
Conventional Band Gap Reference (BGR) and Low Dropout (LDO) circuits in power integrated circuits are susceptible to performance degradation due to supply glitches, leading to issues such as undershoot and reverse current paths, which affect the output voltage and require additional capacitors, impacting overall circuit performance.
Innovation Solution
The integrated circuit employs a cascaded Resistor-Capacitor (RC) filter and switched-capacitor based notch filter in the BGR circuit to average voltage and reduce ripples, while the LDO circuit uses parallel NMOS switches controlled by proportional and differential path signals to prevent reverse current during negative glitches, ensuring a stable output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional BGR circuit with switch cap based notch filter is used, then the circuit can filter average chopping voltage, but the filter passes supply glitches during negative supply glitch conditions and requires filter settling time that degrades glitch detector performance
Solution Approach 1:
The patent employs dynamic switching of filter topologies based on supply conditions. The first filter (switched-capacitor notch filter) operates during normal conditions, while the second filter (RC filter) is activated during negative supply glitch conditions. This dynamic adaptation allows the circuit to maintain reliability across varying supply conditions without compromising glitch detection performance.
Solution Approach 2:
The patent changes the filtering parameters dynamically by switching between two different filter configurations. The switched-capacitor notch filter provides notch filtering at specific frequencies during normal operation, while the RC filter provides broader frequency suppression during glitch conditions. This parameter change enables the circuit to address both normal filtering requirements and glitch suppression requirements.
2Reliability
If a high load capacitor is added to the LDO circuit to stabilize output during reverse current conditions, then the output voltage stability improves, but the circuit complexity increases and other performance metrics are impacted
Solution Approach 1:
The patent introduces an intermediary circuit between the LDO output and the reverse current path. This intermediary consists of detection circuitry that senses reverse current conditions and activates a switching mechanism to block the reverse current flow. This approach provides the necessary stability during reverse current conditions without requiring a large capacitor, thus avoiding the associated complexity and performance trade-offs.
Solution Approach 2:
The patent extracts the reverse current blocking function from the main LDO circuit by implementing it as a separate, dedicated circuit block. This extraction allows the LDO to focus on its primary voltage regulation function while the separate reverse current blocking circuit handles the stability requirement during reverse current conditions, thereby reducing overall circuit complexity.
3Reliability
If an external high load capacitor is implemented to stabilize LDO output during supply glitches, then the output voltage variation is subsidized, but additional pin and pad are required
Solution Approach 1:
The patent nests the stabilization function within the existing LDO circuit structure by integrating the reverse current blocking mechanism and filtering circuits inside the LDO block. This nesting eliminates the need for external capacitors while achieving the same stability effect, thereby avoiding additional pins and pads in the package.
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 provides a glitch-immune intermediate supply voltage, maintaining stable output voltage even during power supply fluctuations, reducing the need for large capacitors and enhancing circuit performance.
Implementation Method 1
a cascaded Resistor-Capacitor (RC) filter and switched-capacitor based notch filter in the BGR circuit to average voltage and reduce ripples
Implementation Method 2
The SC-based notch filter circuit may be employed to further average the voltage output by the cascaded RC filter. The SC-based notch filter circuit helps to filter out unwanted noises or glitches on the input power supply
Implementation Method 3
The LDO circuit uses parallel NMOS switches controlled by proportional and differential path signals to prevent reverse current during negative glitches
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
The present disclosure relates to an integrated circuit for generating an intermediate supply voltage which is immune to glitches on power supply voltage. An example integrated circuit comprises a Band Gap Reference (BGR) circuit configured to generate a reference voltage immune to glitches on a power supply. The integrated circuit also comprises a Low Dropout (LDO) circuit which gets the reference voltage from the BGR circuit. The LDO circuit is configured to generate a glitch immune intermediate supply voltage based on the reference voltage and the power supply which is prone to glitch.