Multi-Domain I/O Driver With NMOS Voltage-Drop Post Driver
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Solution Overview
Problem
Conventional I/O driving circuits operate at a single power domain and cannot meet the requirements of different operating voltages, and the post drivers with PMOSFETs are prone to failure due to control signals generated by the pre-driver, which cannot operate across a wide voltage range.
Innovation Solution
The I/O driving circuit incorporates a post driver with a first switch device and a first voltage providing device that allows for a voltage drop, enabling operation across multiple power domains and using NMOSFETs for a more stable voltage drop function, while the pre-driver generates control signals across different power domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional PMOSFETs with thin oxides are used in the post driver, then the device can operate at core voltage levels, but the transistors may be broken by control signals generated by the pre-driver and cannot operate across a wide voltage range
Solution Approach 1:
The post driver is segmented into multiple independent stages: a first stage with PMOSFETs for voltage inversion and a second stage with NMOSFETs for voltage drop and driving. This segmentation allows each stage to operate within its optimal voltage range and protects the thin-oxide PMOSFETs from high-voltage control signals.
Solution Approach 2:
An intermediate voltage generation stage is introduced between the pre-driver and the final output stage. This intermediate stage acts as a mediator that converts high-voltage control signals into safe low-voltage signals before they reach the thin-oxide PMOSFETs, preventing breakdown while enabling wide voltage range operation.
2Adaptability or versatility
If the pre-driver operates at a single power domain, then the circuit structure is simple, but it cannot meet requirements of different operating voltage for various standards
Solution Approach 1:
The pre-driver is designed with dynamic voltage domain selection capability, allowing it to adaptively operate in different power domains based on the required output voltage level. This dynamic adaptation enables compatibility with multiple standards (e.g., DDR3, DDR4, LPDDR4) without requiring separate dedicated circuits for each standard.
Solution Approach 2:
The pre-driver is designed as a universal block that can function across multiple voltage domains by selecting appropriate control signals and operating modes. This multi-functional design allows a single pre-driver circuit to support various memory standards with different voltage requirements, reducing overall system complexity.
3Stability of the object's composition
If NMOSFETs are used in the pull-up circuit to provide voltage drop, then the driving voltage becomes more stable, but the device complexity increases
Solution Approach 1:
The invention changes the key parameter of the pull-up circuit by using NMOSFETs instead of traditional PMOSFETs. This parameter change exploits the different electrical characteristics of NMOSFETs (higher electron mobility, better voltage drop control) to achieve more stable driving voltage, particularly for high-speed memory interfaces requiring precise voltage levels.
Data Source
AI summary
An I/O driving circuit comprising a post driver. The post driver comprises: a first switch device, comprising a first terminal coupled to an I/O voltage, and comprising a second terminal, wherein the first switch device provides an initial driving voltage at the second terminal of the first switch device; and a first voltage providing device, comprising a first terminal coupled to the second terminal of the first switch device, and comprising a second terminal. The first voltage providing device is configured to provide a driving voltage at the second terminal of the first voltage providing device via providing a voltage drop to the initial driving voltage.