OTP Memory Readout Circuit With Offset Current Subtraction
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Solution Overview
Problem
The increase in circuit area and power consumption, as well as complex timing control, are issues in existing readout circuits for semiconductor devices with One Time Programmable (OTP) cells due to the need for larger clamp elements and increased reference currents.
Innovation Solution
A semiconductor device design that includes a bit line connected to first and second memory cells, a clamp element, a reference current source, a sense amplifier, and an offset current source, which allows for the detection of cell current magnitude by subtracting an offset current from the readout current, thereby reducing the area and power consumption of the clamp element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger clamp element is used to handle the cell current in OTP cells, then the readout operation can be performed, but the circuit area increases
Solution Approach 1:
The current detection function is segmented into multiple components: the clamp element handles only the reference current, while a separate offset current source generates an offset current that is subtracted from the cell current. This segmentation allows the clamp element to be smaller while maintaining readout capability.
Solution Approach 2:
An offset current source is introduced as an intermediary component that generates a compensating current. This offset current mediates between the cell current and the reference current, allowing accurate current detection without requiring the clamp element to handle the full cell current magnitude.
2Reliability
If a larger clamp element is used to handle the cell current in OTP cells, then the readout operation can be performed, but the power consumption increases
Solution Approach 1:
The power consumption is segmented by separating the clamp element's function from the offset current generation. The clamp element consumes power only for generating the reference current, while the offset current source consumes power to generate the compensating current. This segmentation reduces total power consumption compared to using a large clamp element for the full cell current.
3Measurement precision
If increased reference current is used for OTP cell readout, then the cell current detection can be performed, but the timing control becomes complex
Solution Approach 1:
The offset current is generated in advance by the offset current source before the actual current detection occurs. This preliminary generation of the offset current simplifies timing control, as the offset current is ready when needed without requiring complex synchronized timing adjustments.
Data Source
AI summary
A clamp element 46 applies a fixed potential to a bit line BL at a time of a readout operation. A reference current source RCS generates a reference current Iref. An offset current source OCS1 is activated at a time of a readout operation for an OTP cell OTPC, and at a time of being activated, generates an offset current Iof1 to be subtracted from a cell current Icel. At the time of the readout operation for the OTP cell OTPC, the sense amplifier SA detects a magnitude relationship between the reference current Iref and a readout current Ird obtained by subtracting the offset current Iof1 from the cell current Icel.