Wide-Range IO Transceiver Switching for Glitch-Free Mode Transitions
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Solution Overview
Problem
Designing IO circuits for integrated circuits that support multiple IO standards across a wide supply range is challenging due to voltage limitations, leading to glitches during mode transitions between high-voltage and low-voltage operations.
Innovation Solution
A transceiver design that includes a transmitter with a stack of p-channel and n-channel transistors and a receiver with a combination of Schmitt trigger receivers, along with a pad splitter circuit and bias generator, to manage voltage swings and ensure glitch-free operation across both modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two different data paths are used to drive the IO pad in high- and low-voltage modes, then the IO circuit can accommodate multiple IO standards across a wide supply range, but glitches occur at the IO pad and at the output of the receivers when switching between modes due to mismatch in delay for turn-off and turn-on of the two data paths
Solution Approach 1:
The control circuit activates one data path in advance before switching modes, ensuring it is fully ready to operate. This preliminary activation prevents glitches by ensuring the active data path is completely prepared before the transition occurs, addressing the delay mismatch problem between turn-off and turn-on of data paths.
Solution Approach 2:
A control circuit acts as an intermediary between the two data paths, coordinating their switching operations. The control circuit manages the transition by controlling the timing and sequence of switching, ensuring smooth handover between high-voltage and low-voltage modes without causing glitches.
2Adaptability or versatility
If two different receivers are used to receive data from the IO pad in high- and low-voltage modes, then the receiver can operate across a wide supply range, but glitches occur at the IO pad and at the output of the receivers when switching from one mode to the other mode
Solution Approach 1:
The control circuit prepares the upcoming receiver in advance before mode switching, ensuring it is fully initialized and ready to receive data. This preliminary action eliminates glitches at the receiver output by ensuring the active receiver is completely prepared before the transition from high-voltage to low-voltage mode or vice versa.
Solution Approach 2:
The control circuit serves as an intermediary that coordinates the switching between two different receivers. It manages the transition timing and ensures smooth handover, preventing glitches at the receiver output that would otherwise occur during mode switching.
3Ease of operation
If the delay for turn-off and turn-on of the two data paths is not matched, then switching between high- and low-voltage modes is simpler, but undesirable state changes, resets, and functional failures occur due to glitches
Solution Approach 1:
The control circuit incorporates feedback mechanisms to monitor the switching status of data paths and receivers. This feedback allows the control circuit to adjust timing and ensure proper synchronization, maintaining both simplicity of operation and functional correctness during mode transitions.
Solution Approach 2:
The control circuit performs preliminary actions to prepare data paths and receivers before mode switching, ensuring they are ready without requiring complex delay matching. This approach maintains operational simplicity while ensuring reliable transitions without glitches or functional failures.
Data Source
AI summary
An example receiver includes: a pad splitter circuit coupled to a pad, the pad splitter circuit configured to generate a first logic signal and a second logic signal; a wide-range receiver coupled to the pad splitter circuit to receive the first and second logic signals, the wide-range receiver comprising a combination of a first Schmitt trigger receiver and a second Schmitt trigger receiver; a control circuit coupled to the pad splitter circuit and the wide-range receiver; and a bias generator circuit coupled to the pad splitter circuit and the wide-range receiver.