Output Buffer Capacitance Switching for Slew Rate and Power Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional output buffers in integrated circuit devices experience high peak current and power noise due to simultaneous switching, leading to unacceptable voltage drops and electromagnetic interference, necessitating control over slew rate and increased power noise immunity.
Innovation Solution
An output buffer with a capacitance circuit that can be configured into either a slew rate configuration to reduce the slew rate of the buffered output signal or a decoupling configuration to enhance power noise immunity, allowing for programmable slew rate and increased immunity through capacitive coupling in a feedback path or between power and ground potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If transistor sizing in the inverter chain is optimized for driving external loads, then the output buffer can drive resistive-capacitive-inductive loads effectively, but the slew rate becomes high causing high peak current and simultaneous switching issues
Solution Approach 1:
The patent implements dynamic slew rate control by making the capacitance value adjustable through control signals. The output buffer transitions between different capacitance states (first capacitance value for normal operation, second capacitance value for slew rate reduction) based on operating conditions, allowing the system to adaptively control the slew rate rather than using a fixed value. This dynamic adjustment resolves the contradiction by enabling high driving capability when needed while reducing peak current and EMI when slew rate control is required.
Solution Approach 2:
The patent changes the capacitance parameter of the capacitance circuit based on control signals to achieve different operational modes. By varying the capacitance value between a first capacitance value (providing normal buffering) and a second capacitance value (reducing slew rate), the system can optimize performance for different conditions. This parameter change approach allows the output buffer to maintain driving capability while controlling harmful effects like peak current and electromagnetic interference.
2Power
If multiple output buffers switch simultaneously to provide high output current, then the integrated circuit device can drive heavy loads, but power noise increases causing unacceptable voltage drop in power supply
Solution Approach 1:
The patent implements dynamic control of the capacitance circuit to manage simultaneous switching of multiple output buffers. By adjusting the capacitance value in response to control signals, the system can coordinate buffer switching operations to reduce power noise while maintaining the ability to provide high output current when required. This dynamic adjustment prevents unacceptable voltage drops in the power supply during heavy load conditions.
3Device complexity
If a fixed capacitance value is used in the capacitance circuit, then the circuit structure is simple, but the slew rate cannot be programmatically controlled for different operating conditions
Solution Approach 1:
The patent implements a multi-functional capacitance circuit that can operate in different modes based on control signals. The same capacitance circuit structure serves multiple purposes: providing normal buffering with a first capacitance value and reducing slew rate with a second capacitance value. This universal design allows the circuit to adapt to different operating conditions without requiring entirely separate circuits for each function, balancing complexity with versatility.
4Object-generated harmful factors
If the capacitance circuit is always configured for slew rate reduction, then peak current and EMI are reduced, but power noise immunity decreases when the capacitor should be used for decoupling
Solution Approach 1:
The patent implements dynamic reconfiguration of the capacitance circuit between slew rate reduction mode and decoupling mode based on operational requirements. The control signals enable the circuit to switch between using the capacitor for reducing slew rate (when peak current and EMI are concerns) and for providing decoupling capacitance (when power noise immunity is needed). This dynamic switching resolves the contradiction by ensuring the capacitor serves the most appropriate function at any given time.
Solution Approach 2:
The patent employs control signals that respond to operational conditions to adjust the capacitance circuit configuration. This feedback mechanism allows the system to monitor when slew rate control is needed versus when decoupling capability is required, and automatically reconfigure the capacitance circuit accordingly. The feedback-based control ensures optimal performance by preventing the use of slew rate reduction configuration when decoupling would be more beneficial for power noise immunity.
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 effectively reduces slew rates and increases power noise immunity, mitigating peak current and electromagnetic interference issues, thereby improving the performance and reliability of integrated circuit devices.
Implementation Method 1
the capacitance circuit electrically couples the capacitor between a power potential and a ground potential of the output buffer for increasing the power noise immunity of the output buffer
Implementation Method 2
the capacitance circuit electrically couples a capacitor of the capacitance circuit in a feedback path for reducing a slew rate of a buffered output signal generated by the output buffer
Data Source
AI summary
An integrated circuit device includes an output buffer having a capacitance circuit configurable in a slew rate configuration or a decoupling configuration. In the slew rate configuration, the capacitance circuit electrically couples a capacitor of the capacitance circuit in a feedback path for reducing a slew rate of a buffered output signal generated by the output buffer. In the decoupling configuration, the capacitance circuit electrically couples the capacitor between a power potential and a ground potential of the output buffer for increasing power noise immunity of the output buffer. The output buffer may have more than capacitance circuit, each of which is individually configurable into the slew rate configuration or the decoupling configuration.