Pre-charge Transistor Control for Low Power Memory
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Solution Overview
Problem
Memory devices with pre-charge transistors in global data line drivers experience increased power consumption due to small but significant current flow even in standby states, especially when operating in low voltage modes.
Innovation Solution
The pre-charge transistor is only activated when the memory device is in an active state and operating in low voltage mode, or when the device is in standby but reading a high datum, ensuring it remains off in other cases to minimize current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-charge transistor is added to the global data line driver to prevent voltage drop errors in low voltage mode, then data transfer reliability is improved, but power consumption increases due to current flow through the pre-charge transistor even in standby state
Solution Approach 1:
The pre-charge transistor is made dynamic by controlling its activation state based on operational conditions. It is enabled only during active read operations in low voltage mode (when DOEN is high and SUPPLY18 is high), and disabled during standby state or high voltage mode, transforming it from a static always-on component to a conditionally activated one that adapts to system state
Solution Approach 2:
The control signal PRE_N is modified to incorporate additional control conditions beyond the basic read operation signal. By ANDing PRE_N with both DOEN (read operation enable) and SUPPLY18 (low voltage mode select), the pre-charge transistor's activation parameters are changed to respond only to the specific combination of low voltage mode and active read operation, eliminating unnecessary current flow in other states
2Speed
If the pre-charge transistor remains on during standby state to maintain readiness, then response time is improved, but power consumption increases due to continuous current flow
Solution Approach 1:
The pre-charge transistor performs preliminary action by charging the input line of the global data line driver before the actual read operation begins. When a read operation is initiated (DOEN goes high), the pre-charge transistor is already enabled and has prepared the voltage levels, ensuring immediate response without waiting for standby maintenance
Solution Approach 2:
The pre-charge transistor operates periodically rather than continuously, being activated only during actual read operations and disabled during standby periods. This periodic activation pattern, controlled by the DOEN signal, maintains response readiness when needed while eliminating continuous power consumption during idle states
Data Source
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AI summary
Memory devices that include a pre-charge transistor for connecting/disconnecting the input line of the global data line driver to a supply voltage line are more power consuming than the memory devices that do not include it because of a small though significant flow of current through the pre-charge transistor even in stand-by state. This problem is solved with a method implemented in a novel memory device, by turning on the pre-charge transistor only when, at the same time, the enabling signal of the page buffer is asserted, a low voltage functioning mode is selected and the memory device is not in a stand-by state, or the memory device is in a stand-by state but the datum read from the memory is high. The pre-charge transistor is securely turned off in all other cases.