Standby Charge Pump Voltage Shifter for Memory Arrays
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Solution Overview
Problem
High standby current consumption in charge pump systems for high-density memory arrays due to unstable read voltage generation and significant DC current leakage, which impacts power efficiency and increases process costs and circuit area.
Innovation Solution
Incorporation of a capacitor-based voltage shifter and transistor circuitry that blocks DC current and maintains a stable voltage level, using a field-effect transistor to operate in saturation and counteract charge leakage, with periodic refresh rates determined by the charge pump output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Zener diode or resistive voltage divider is used in the voltage detector to convert voltage levels, then voltage detection is enabled, but DC current is drained from the charge pump output which increases standby current consumption
Solution Approach 1:
The patent implements periodic refresh operation where the charge pump is enabled only when the voltage on the RDPWR node falls below the target read voltage VRD. The voltage detector uses a capacitor that is periodically charged to VRD and then used to detect voltage drops, rather than continuously draining current through Zener diodes or resistive dividers. This periodic action maintains detection capability while dramatically reducing standby current consumption.
2Measurement precision
If a resistive voltage divider is used to convert voltage levels, then voltage detection is achieved, but large resistors entail large circuit area and large parasitic capacitance which slows response time
Solution Approach 1:
The patent extracts the voltage level conversion function from the continuous resistive voltage divider and implements it using a capacitor that is periodically charged to the target voltage VRD. This capacitor-based approach replaces the large resistors and their associated parasitic capacitance with a smaller capacitor that is refreshed periodically, thereby reducing circuit area and improving response time while maintaining detection accuracy.
3Stability of the object's composition
If the charge pump is continuously enabled to maintain stable read voltage, then voltage stability is improved, but standby current consumption increases due to repeated high voltage generation
Solution Approach 1:
The charge pump operates periodically rather than continuously. A capacitor is charged to the target read voltage VRD and then used to detect when the RDPWR node voltage drops below VRD due to leakage. The charge pump is enabled only at these moments to replenish the leaked charge, rather than continuously generating high voltage. This periodic operation maintains voltage stability while dramatically reducing standby current consumption.
Solution Approach 2:
The capacitor is pre-charged to the target voltage VRD before the detection phase. This preliminary action allows the system to quickly detect voltage drops without requiring continuous charge pump operation, enabling fast response to leakage events while minimizing overall power consumption during standby periods.
4Power
If a stronger charge pump is used to support read current during read operations, then read current capability is improved, but voltage overshoot occurs during refresh phase due to fast voltage ramping
Solution Approach 1:
The system dynamically adjusts the charge pump operation based on detected voltage conditions. The charge pump strength and duration are modulated according to the actual voltage drop detected, rather than operating at fixed maximum strength. This dynamic control prevents voltage overshoot during refresh while maintaining sufficient read current capability when needed, achieving both power efficiency and voltage stability.
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
Significantly reduces voltage fluctuation and DC current drain, enhancing power efficiency and reducing process costs by minimizing parasitic capacitance and improving response time, while maintaining accurate read operations.
Implementation Method 1
The voltage shifter includes a capacitor having a first terminal coupled to the charge pump output, and a second terminal. The capacitor shifts a first voltage level at the first terminal to a second voltage level at the second terminal.
Implementation Method 2
The voltage shifter blocks dc current from the charge pump output through the voltage shifter.
Implementation Method 3
The charge pump circuitry includes a weaker charge pump periodically enabled by signal ENPMP. The weaker charge pump is active when the detected voltage on the RDPWR node is less than the target read voltage VRD.
Data Source
AI summary
In one aspect, a charge pump output of a charge pump is coupled to a capacitor of a voltage shifter. The output of the voltage shifter causes pump control logic to enable the charge pump. In another aspect, a transistor in saturation has a drain terminal coupled to a charge pump output and a source terminal coupled to an output mode providing a word line read voltage.