Memory Oscillator Calibration Using Fuse-Based Refresh Timing
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Solution Overview
Problem
Semiconductor memory oscillators exhibit cycle variations due to process variations, requiring individual adjustments of refresh time for each chip, which is time-consuming and inaccurate in existing methods.
Innovation Solution
A method and device for adjusting the oscillation cycle of a refresh request signal by using a test circuit to set a constant-current or constant-voltage value, which is then used by an oscillator to generate a signal that is divided by a frequency divider to produce a refresh request signal of a desired cycle, with the frequency division number being written into a fuse circuit for later use in normal mode to maintain the desired cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual adjustment of refresh time is conducted for each semiconductor chip, then the variation in required refresh time is reduced, but the adjustment process becomes time-consuming
Solution Approach 1:
The patent applies preliminary action by measuring and determining the oscillation cycle of each chip's oscillator during the probing test phase before mass production. The frequency division number is calculated and stored in advance based on these measurements, so that during normal operation, each chip can directly use its pre-determined frequency division number without requiring time-consuming individual adjustments. This resolves the contradiction by performing the precision-adjustment work beforehand.
Solution Approach 2:
The patent implements self-service by enabling each semiconductor chip to autonomously generate its own refresh request signal using its individually measured oscillation cycle characteristics. During probing test, each chip's oscillator cycle is measured and the corresponding frequency division number is automatically determined and stored in that chip's fuse circuit. In normal operation, each chip independently uses its stored frequency division number to generate refresh requests without external intervention, eliminating the need for continuous individual adjustments.
2Manufacturing precision
If frequency division number is changed for every semiconductor chip based on oscillation cycle measurement, then refresh time variation is reduced, but the device complexity increases
Solution Approach 1:
The patent extracts the individual adjustment functionality from the main memory circuit by implementing a separate probing test mode. During probing test, a test circuit measures the oscillation cycle and determines the frequency division number, which is then stored in the fuse circuit. In normal mode, the main memory circuit simply reads the pre-stored frequency division number without requiring complex real-time adjustment mechanisms. This separation reduces device complexity while maintaining precision.
Solution Approach 2:
The patent changes the operating parameters of the oscillator by adjusting the frequency division number based on measured oscillation cycle characteristics. Each chip's oscillator operates at a specific frequency determined during probing test, and the frequency division number is selected to compensate for process variations. This parameter adjustment approach achieves precise refresh timing without requiring complex hardware modifications to the core oscillator circuit.
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
This approach allows for accurate measurement and adjustment of the oscillation cycle in one measurement, reducing variations and extending the measurement time, enabling precise generation of the refresh request signal.
Implementation Method 1
an oscillator to generate a self-refresh request signal. The oscillator creates variations in the cycle of the oscillation due to process variations.
Data Source
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AI summary
An oscillating device (101) including: an oscillator (105) generating an oscillation signal (S1) according to an enable signal (ST); a counter (106) counting an oscillation number of the oscillation signal (S1) and being able to reset at the oscillation number indicated by a first signal; and a comparator (107) comparing the counted oscillation number (S3) and a reference number (CNT), is provided. The device may further comprise fuse circuits (102) for calibration of the oscillator in accordance with temperature.