Charge Pump Efficiency Testing Using Cascaded Clock Edge Counting
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Solution Overview
Problem
Existing methods for determining charge pump efficiency in NAND flash memory are inaccurate and limited to measuring a few chips, as they require direct measurement of input and output currents, which is difficult and not suitable for wafer-level assessment.
Innovation Solution
A charge pump test configuration and method that calculates efficiency by determining the ratio of clock edges in a cascaded setup, allowing for relative input current determination without direct current measurement, enabling more accurate and wafer-level efficiency assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct measurement of input and output currents is used to determine charge pump efficiency, then measurement accuracy may be improved, but the complexity of the measurement system and difficulty of operation increase significantly
Solution Approach 1:
The patent introduces a mediator charge pump that indirectly measures the efficiency of the target charge pump. Instead of directly measuring input and output currents of the target charge pump, the mediator charge pump converts these current measurements into clock edge counts, which are easier to measure accurately. The mediator charge pump acts as an intermediary device that transforms the measurement problem from direct current measurement to clock edge counting.
Solution Approach 2:
The patent replaces the mechanical/electrical current measurement system with a timing-based clock edge counting system. By substituting direct current measurement with clock cycle counting, the system achieves comparable or better measurement precision while reducing operational complexity. The clock edge count serves as a proxy for current measurement.
2Measurement precision
If direct current measurement methods are used, then efficiency determination may be more accurate, but the ease of operation and applicability to wafer-level assessment deteriorates
Solution Approach 1:
The mediator charge pump enables wafer-level assessment by converting complex current measurements into simple clock edge counts that can be rapidly acquired across multiple chips. This intermediary approach maintains measurement accuracy while dramatically improving ease of operation and scalability to wafer-level testing.
Solution Approach 2:
The patent changes the measurement parameter from direct current values to clock edge counts. This parameter transformation maintains the essential information needed for efficiency calculation while making the measurement process much easier to perform at scale across wafer-level production testing.
3Ease of operation
If clock edge counting method is used to determine efficiency, then ease of operation and wafer-level assessment capability improve, but direct measurement precision may be affected
Solution Approach 1:
The mediator charge pump compensates for any potential precision loss by providing a calibrated transformation between current and clock edge count. The mediator device ensures that the indirect measurement through clock counting remains accurately correlated with the actual current values, preserving measurement precision while gaining operational ease.
Solution Approach 2:
The system uses feedback from the mediator charge pump's operation to校准 the relationship between clock edge counts and actual current values. By monitoring the mediator's performance and adjusting accordingly, the system maintains high measurement precision despite using the indirect clock counting method.
Data Source
AI summary
A charge pump test configuration and corresponding method of operation are disclosed for determining charge pump efficiency without needing to obtain direct current measurements. A first number of clock edges (CEs) of a clock signal supplied to a first charge pump is determined over a period of time for a predetermined output current. The first charge pump is then connected with a charge pump under test (PUT) in a cascaded manner such that an output current of the first charge pump is supplied to the PUT as an input current. A second number of CEs of a clock signal supplied to the first charge pump is determined over the same period of time for the same predetermined output current from the PUT. The efficiency of the PUT can then be determined as the ratio of the first number of CEs to the second number of CEs, or vice versa.