5 Volt Tolerant Voltage Regulator for USB Transceiver Short Circuit Protection
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Solution Overview
Problem
USB transceiver circuitries face damage from short circuits to 5 volt sources due to inadequate protection in fine line CMOS technologies, where transistor breakdown voltage is less than 5 volts, necessitating a solution to prevent damage from extended short circuit exposure.
Innovation Solution
A voltage regulator circuit incorporating an error amplifier, feedback circuit, driver circuit, and short circuit protection circuitry that selectively protects transistors within the error amplifier, feedback amplifier, and driver circuit, enabling the USB interface pins to withstand short circuits to a 5 volt source by maintaining the voltage below 3.6 volts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fine line CMOS technology is used to reduce manufacturing cost and improve integration, then manufacturing precision and productivity are improved, but the transistor breakdown voltage becomes less than 5 volts making the circuit vulnerable to 5 volt short circuits
Solution Approach 1:
A voltage regulator circuit is introduced as an intermediary component between the 5 volt input source and the fine line CMOS circuitry. The regulator includes a driver circuit that limits the voltage presented to internal transistors, and a short circuit protection circuit that detects and responds to short circuit conditions by controlling the driver circuit to prevent damage to the vulnerable fine line CMOS transistors
Solution Approach 2:
The voltage regulator dynamically changes the voltage parameter from the 5 volt input to a controlled lower voltage (maintaining below 3.6 volts) that is safe for fine line CMOS transistors. The short circuit protection circuitry monitors voltage and current parameters and adjusts the driver circuit operation to maintain safe operating conditions during short circuit events
2Reliability
If 5 volt tolerant circuitry is used to protect against short circuits, then reliability is improved, but the transistor breakdown voltage must be increased which is not feasible in fine line CMOS processes
Solution Approach 1:
The voltage regulator serves as a protective intermediary that allows fine line CMOS circuitry to operate in 5 volt environments without requiring the transistors themselves to be 5 volt tolerant. The regulator isolates the vulnerable transistors from 5 volt stress by controlling the voltage they experience, enabling the use of cost-effective fine line CMOS processes while achieving 5 volt short circuit tolerance
3Ease of operation
If the USB transceiver pins are exposed to 5 volt sources during short circuits, then ease of operation is maintained, but the internal circuitry is damaged due to inadequate protection
Solution Approach 1:
The short circuit protection circuitry is designed to detect potential short circuit conditions and activate the driver circuit to limit voltage and current before damage can occur to the internal circuitry. The protection mechanism is preemptive, continuously monitoring and ready to respond to short circuit events on the USB pins, allowing the pins to be exposed to 5 volt sources without risking internal damage
Data Source
AI summary
A voltage regulator circuit comprises an error amplifier for generating, an error signal responsive to a reference voltage in a feedback signal. A feedback circuit provides the feedback voltage signal to the error amplifier and a driver circuit provides regulated output voltage responsive to the input voltage in the error signal. Short circuit protection circuitry selectively protects transistors within the error amplifier, the feedback amplifier and the driver circuit responsive to a short circuit protection enablement signal.