Word Line Control Circuit Leakage Reduction
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Solution Overview
Problem
Conventional word line control circuits for semiconductor memories face significant leakage currents and high power consumption in both active and standby modes, especially exacerbated by high temperatures, due to sub-threshold current and voltage level drops in word lines.
Innovation Solution
The proposed solution involves a VSSB coupling device and word line driver system that utilize P-channel and N-channel transistors, along with inverters, to dynamically switch between VBB and VSS voltages, eliminating gate-source cross voltages and reducing leakage currents by maintaining VSS at the VSSB output terminal in standby mode and applying VBB during access, thereby minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional word line drivers are used in standby mode with P-channel transistors turned on to maintain word line voltage, then word line voltage is maintained, but significant leakage current flows from VSS to VBB due to gate-source cross voltage
Solution Approach 1:
The patent changes the voltage parameter at the VSSB output terminal from ground (0V) to a boosted positive voltage (VPP, e.g., 1.5V) during standby mode. This parameter change eliminates the gate-source cross voltage (VGS = VSS - VBB = 0 - (-0.35V) = 0.35V) that causes leakage current, while still maintaining word line voltage through the turned-on P-channel transistors.
2Use of energy by stationary object
If N-channel transistors are turned off in standby mode to reduce power consumption, then power consumption is reduced, but voltage level drop occurs in VBB due to sub-threshold current
Solution Approach 1:
The patent changes the VSSB output terminal voltage from ground to a boosted positive voltage (VPP) during standby mode. This eliminates the gate-source cross voltage (VGS = VSS - VBB = 0 - (-0.35V) = 0.35V) that causes sub-threshold leakage current through N-channel transistors, thereby preventing VBB voltage level drop while maintaining low power consumption.
3Device complexity
If multiple word line drivers are grouped together to reduce device complexity, then device complexity is reduced, but excessive power is consumed in standby state due to multiple drivers remaining active
Solution Approach 1:
The patent applies a boosted positive voltage (VPP) at the VSSB output terminal during standby mode, which turns off the N-channel transistors in all word line drivers in the group. This enables multiple drivers to be grouped together while consuming minimal power in standby state, as all drivers share the same low-power standby condition.
4Ease of operation
If VSSB coupling device outputs ground voltage in standby mode, then word line drivers receive proper bias, but non-zero gate-source cross voltage creates leakage current from VSS to VBB
Solution Approach 1:
The patent changes the VSSB output terminal voltage from ground (0V) to a boosted positive voltage (VPP, e.g., 1.5V) during standby mode. This parameter change eliminates the gate-source cross voltage (VGS = VSS - VBB = 0 - (-0.35V) = 0.35V) that causes leakage current, while word line drivers still receive proper bias through the turned-on P-channel transistors.
Data Source
AI summary
A word line control device has a word line driver for deactivating and activating a word line to control access to a memory cell, and a voltage coupling device for coupling voltages to the word line driver. The word line control device maintains boosted voltages and has significantly reduced leakage currents and power consumption in the active and standby modes.