5V Tolerant CML Transceiver Circuit Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current CML transceiver circuits operating at lower supply voltages are vulnerable to signal spikes from circuits with higher supply voltages, leading to potential malfunction and damage due to over-stressing of components like MOSFETs and diodes.
Innovation Solution
A high-voltage tolerant transceiver circuit design that incorporates NMOS transistors with their gates coupled to a low power supply and substrates grounded, along with substrate and bias isolating circuits to prevent drain voltage from exceeding the low voltage supply, thereby protecting components from high-voltage signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If AC-coupled CML transceiver operates at lower supply voltage (2.5V), then power consumption and signal integrity are improved, but vulnerability to high-voltage signal spikes (5V) increases causing component damage
Solution Approach 1:
The patent introduces NMOS transistors as intermediary protective elements between the high-voltage external interface and the low-voltage internal circuitry. These transistors act as voltage-limited switches that allow normal signal passage while blocking damaging high-voltage spikes, thus mediating the conflict between low-voltage operation and high-voltage tolerance
Solution Approach 2:
The patent changes the voltage parameter handling by using transistors with gate-source voltage clamping. The transistor gates are held at a fixed low voltage potential while sources connect to external pads, creating a voltage threshold that automatically limits the voltage differential across internal components regardless of external voltage conditions
2Reliability
If NMOS transistors are added for high-voltage protection, then reliability against signal spikes is improved, but device complexity increases
Solution Approach 1:
The patent segments the transceiver circuit into protected internal blocks and external interface pads, with protective NMOS transistors placed at strategic interface points. This segmentation allows the core functional blocks to remain simple while adding protection only where voltage transitions occur, minimizing overall complexity increase
Solution Approach 2:
The protective NMOS transistors are configured to automatically activate when voltage exceeds safe thresholds, using the voltage spike itself to turn on the protection mechanism. The transistor gates are biased such that normal operation keeps them off, but high-voltage conditions automatically enable them, providing self-regulating protection without external control circuits
Data Source
AI summary
A high voltage tolerant transceiver operating at a low voltage is provided, including two input/output pads to receive a receive signal and transmit a transmit signal; a transmitter block to transmit the transmit signal; a receiver block to receive the receive signal and provide an amplified signal; at least one of the transmitter block and the receiver block further comprising at least two NMOS transistors having their gate coupled to a low power supply to receive the low voltage, their substrate coupled to ground, and their source coupled to the input/output pad. Also provided is a circuit to isolate the output of a transmitter from high voltages, including a first transistor and a second transistor. Also provided is a substrate isolating circuit, including a first transistor, a second transistor, and a third transistor so that the substrate voltage is isolated from a high voltage in the pads. Further provided is a bias isolating circuit so that an input bias voltage is isolated from a high voltage in the pads.