D/A Decoder Split PMOS-NMOS Switching to Cut Transistor Count
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Solution Overview
Problem
Conventional digital to analog (D/A) converters used in display drivers require a high number of transistors, leading to increased power consumption and space occupation, which is undesirable in modern, miniaturized electronic devices.
Innovation Solution
The use of P-type and N-type transistor switches instead of CMOS switches, with each P-type and N-type switch formed of fewer transistors, reducing the overall transistor count, and implementing a method where an n-bit D/A decoder includes an n−1 bit PMOS decoder for output voltages above a threshold and an n−1 bit NMOS decoder for output voltages below a threshold, with a selector to choose between them based on the input digital signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CMOS switches are used in D/A decoders, then reliable digital to analog conversion is achieved, but transistor count increases leading to higher power consumption and space occupation
Solution Approach 1:
The decoder is divided into two separate decoders: a first decoder using P-type transistors for generating analog voltages above a threshold, and a second decoder using N-type transistors for generating analog voltages below a threshold. This segmentation allows each decoder to operate in its optimal voltage range while reducing the transistor count compared to using CMOS switches throughout.
Solution Approach 2:
Different types of transistor switches are used in different parts of the decoder circuit based on local requirements. P-type transistor switches are used where high-side switching is needed (above threshold), while N-type transistor switches are used where low-side switching is needed (below threshold), optimizing performance and reducing overall complexity.
2Ease of operation
If more transistors are used in D/A decoder switches, then switching performance is improved, but power consumption and space occupation increase
Solution Approach 1:
The invention extracts and removes unnecessary transistors from the switch configuration by using simple P-type or N-type transistor switches instead of complex CMOS switches. Each P-type and N-type switch is formed of fewer transistors, reducing the overall transistor count while maintaining adequate switching performance for the application.
Data Source
AI summary
An n bit D/A decoder is formed using P-type and N-type transistor switches, instead of convention CMOS switches. Each P-type and N-type switch may be formed of fewer transistors than those used to form a CMOS switch, thereby reducing the overall transistor count. The decoder may be used to decode digital values to non-linear GAMMA corrected analog output voltages.