Semiconductor Memory Self-Refresh Period Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor memory devices face challenges in accurately measuring the self-refresh period due to its short duration and the large errors caused by process, voltage, and temperature variations, especially in low power DRAMs, making it difficult to monitor and analyze using conventional methods.
Innovation Solution
A semiconductor memory device is designed with a self-refresh ring oscillator, a shift register, a multiplexer, and an output buffer to generate and output a self-refresh period level signal, allowing for easy monitoring of the self-refresh period in test mode, enabling accurate measurement using a tester or oscilloscope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a short pulse representing the self-refresh period is outputted through an output pin in a test mode according to the prior art, then the self-refresh period can be measured, but the measurement is difficult due to the very short period ranging from tens of microseconds to hundreds of microseconds
Solution Approach 1:
The self-refresh period measurement is segmented into multiple clock cycles. Instead of measuring a single short pulse, the invention divides the measurement into discrete time segments using a shift register that captures the state of the self-refresh enable signal at each clock cycle, making the measurement process manageable and accurate
Solution Approach 2:
A shift register is introduced as an intermediary component between the self-refresh enable signal and the output buffer. This shift register accumulates and transfers the signal state over multiple clock cycles, effectively bridging the gap between the short self-refresh period and the measurement capability of external testing equipment
2Adaptability or versatility
If a ring oscillator is configured with transistors and resistors for self-refresh, then the self-refresh operation can be performed, but large errors occur in the self-refresh period due to variations of process, voltage and temperature
Solution Approach 1:
The invention implements a feedback mechanism where the self-refresh enable signal generated by the ring oscillator is fed back through a shift register and multiplexer to the output buffer. This allows the actual self-refresh period to be monitored and measured, enabling feedback control to compensate for PVT variations and improve measurement accuracy
Data Source
AI summary
A semiconductor memory device is provided. The semiconductor memory device includes: an oscillation means for generating a self-refresh enable signal and a self-refresh period pulse having a predetermined period in response to a self-refresh signal; a shift register for generating a self-refresh period level signal maintaining a different level at every self-refresh period defined by the self-refresh enable signal and the self-refresh period pulse, in response to a test mode signal; a multiplexing means for selectively outputting a data signal and the self-refresh period level signal in response to the test mode signal; and an output buffer for buffering the output signal of the multiplexing means to output the buffered signal.