On-Chip Reverse Voltage Protection Circuit for ICs
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Solution Overview
Problem
Existing integrated circuits face damage from reverse power connections due to high reverse currents caused by parasitic diodes and ESD structures, which are not adequately protected by off-chip circuits, especially when power supply voltages vary widely from 2V to 40V.
Innovation Solution
An on-chip protection circuit with a PMOS transistor and zener diode configuration that provides low impedance during correct power connections and high voltage blocking during reverse connections, combined with an ESD protection circuit to prevent damaging currents, ensuring safe voltage levels for internal circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor is used to limit reverse current, then reverse current is limited to a lower value, but normal current is also limited reducing power delivery capability
Solution Approach 1:
The protection circuit dynamically changes its impedance characteristics based on voltage polarity. During reverse voltage conditions, the circuit presents high impedance to limit reverse current. During normal forward voltage conditions, the circuit transitions to low impedance to allow full current delivery. This dynamic adaptation resolves the contradiction by having the circuit exhibit different electrical properties depending on the operating condition.
Solution Approach 2:
The circuit changes its electrical parameters (impedance state) based on the voltage condition. The protection transistor switches between on and off states, and the circuit transitions between high-impedance and low-impedance configurations. This parameter change allows the circuit to limit reverse current while maintaining full power delivery capability during normal operation.
2Reliability
If a diode is used for reverse protection, then reverse current is blocked, but voltage drop reduces available voltage especially at low VDD
Solution Approach 1:
The protection circuit dynamically activates the protection function only when reverse voltage is detected. During normal forward voltage operation, the protection transistor is off and the circuit presents minimal impedance, avoiding any voltage drop. When reverse voltage occurs, the transistor switches on to block the reverse current. This dynamic behavior eliminates the continuous voltage drop problem of static diode-based solutions.
Solution Approach 2:
The circuit changes its voltage characteristics based on operating condition. The protection mechanism only introduces voltage drop when actually needed (reverse voltage condition). During normal operation, the circuit maintains full voltage availability by keeping the protection elements in a non-conducting state, thus resolving the voltage drop issue.
3Object-affected harmful factors
If high resistance is used to limit reverse current, then reverse current is better limited, but normal current capability is reduced
Solution Approach 1:
The protection function is segmented from the power delivery function. The circuit uses switching elements to separate the reverse protection path from the normal power path. During reverse voltage, the protection segment is activated to limit current. During normal operation, the protection segment is deactivated and does not interfere with power delivery. This segmentation allows both functions to operate optimally at different times.
Solution Approach 2:
The protection circuit introduces switching transistors as intermediary elements between the power source and the load. These intermediaries can selectively connect or disconnect the protection elements based on voltage polarity. The switching action allows the high-value protection resistors to be included in the circuit only when needed, while maintaining low-impedance power delivery during normal operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively limits current and maintains safe voltage levels during both normal and reverse power connections, protecting internal circuits from damage and ensuring reliable operation across a wide range of power supply voltages.
Implementation Method 1
A zener diode ZD is used to limit the voltage across the M1 gate to prevent breakdown
Implementation Method 2
parasitic diodes of the internal circuits and even ESD (Electronic Static Discharge) circuits can be forward biased and draw a large current
Data Source
AI summary
A voltage protection circuit that has a protection transistor coupled between a voltage supply pin of an integrated circuit and a voltage output terminal of the integrated circuit. A biasing circuit is coupled to a control node of the protection transistor and configured to cause the protection transistor to turn on to form a low impedance path between the voltage supply pin and the voltage output terminal when a positive supply voltage is coupled to the voltage supply terminal and to cause the protection transistor to turn off when a negative supply voltage is coupled to the voltage supply terminal. An electro-static discharge (ESD) protection circuit may also be connected between the voltage supply pin and a reference node that is configured to conduct a negative static discharge current for period of time, and to not conduct a negative current continuously.