RC Delay Circuit With PVT Compensation for Stable Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing RC-based delay elements in memory devices, such as DRAM, experience significant variations in delay due to process, voltage, and temperature (PVT) variations, leading to inefficiencies and inconsistencies.
Innovation Solution
A delay circuit is designed with a first compensation circuit to track and adjust for inverter threshold voltage variations across PVT, and a second compensation circuit to address temperature effects on the resistor and capacitor, using a charge-current coupling circuit to provide a compensation current that reduces delay interval variations across PVT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an RC network is used for delay elements, then chip space efficiency is improved, but delay variation across PVT increases to 30%-35%
Solution Approach 1:
The patent adjusts the threshold voltage of inverters by controlling the gate voltage of compensation transistors (e.g., transistor 121) to counteract PVT variations. By dynamically changing the electrical parameters (threshold voltage, gate voltage) of the compensation circuit components, the delay variation is reduced from 30%-35% to less than 10% across PVT conditions.
2Reliability
If compensation circuits are added to reduce PVT variations, then delay stability is improved, but device complexity increases
Solution Approach 1:
The compensation circuit is merged with the existing RC delay structure by integrating compensation transistors (e.g., transistor 121) that share common nodes and signals with the delay path. The compensation transistor gate is connected to the inverter output, and its source/drain are connected to the RC network nodes, allowing the compensation function to be embedded within the existing circuit topology rather than adding completely separate compensation blocks.
Solution Approach 2:
The compensation transistor automatically adjusts its operating point based on the inverter output signal it receives. The inverter output directly controls the gate voltage of the compensation transistor, which in turn self-adjusts the threshold voltage of the inverter to compensate for PVT variations. This self-regulating mechanism reduces the need for external control circuits and manual calibration, simplifying the overall system while maintaining delay stability.
Data Source
AI summary
Apparatus and methods for a delay circuit are provided. In an example, a delay circuit can include a resistor configured to receive a compensation current, a capacitor configured to receive a charge current based on the compensation current, a first compensation circuit configured to provide a control signal, and a charge-current coupling circuit. The first compensation circuit can include an inverter circuit configured to track an inverter threshold voltage across process, voltage and temperature variations, wherein an output of the inverter circuit is directly coupled to an input of the inverter circuit, and an amplifier configured to receive the output of the inverter circuit an provide the control signal. The charge-current coupling circuit can be configured to receive the control signal and to provide the compensation current and the charge current.