Output Driver Power Down Protection via Parasitic Bipolar Structure
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Solution Overview
Problem
Driver circuits in integrated circuits are vulnerable to damage from high voltage ramps during power down modes, which can cause latch-up effects and excessive current conduction due to the lack of protection against high voltage swings.
Innovation Solution
A low-side driver circuit with a parasitic bipolar structure having a high breakdown voltage is designed to suppress latch-up effects of the parasitic silicon-controlled rectifier (SCR) structure, allowing it to withstand high voltage swings and prevent excessive current conduction during power down operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driver circuit operates without protection during power down mode, then the circuit can be simple and easy to manufacture, but the circuit becomes vulnerable to damage from high voltage ramps and latch-up effects
Solution Approach 1:
The patent introduces a parasitic bipolar structure as an intermediary element within the driver circuit that mediates between the high voltage ramp from the load and the sensitive circuit components. This parasitic structure acts as a protective mediator by clamping the voltage swing and preventing direct exposure of the driver circuit to harmful high voltage conditions during power down mode.
Solution Approach 2:
The patent converts the harmful high voltage ramp into a beneficial protective mechanism by utilizing the parasitic bipolar structure's breakdown characteristics. When exposed to high voltage swings during power down, the parasitic structure enters breakdown mode, which actually protects the main driver circuit by limiting the voltage stress and preventing latch-up effects, thus transforming the harmful voltage spike into a protective clamping action.
2Strength
If the driver circuit uses standard breakdown voltage, then the circuit can operate normally during active modes, but it cannot withstand high voltage swings during power down operations
Solution Approach 1:
The patent applies local quality by creating a specific parasitic bipolar structure with elevated breakdown voltage characteristics at the critical node where high voltage swings occur during power down. This localized enhancement of breakdown voltage strength does not affect the normal operation of the driver circuit during active modes, as the parasitic structure remains dormant under normal operating conditions and only activates when exposed to abnormal high voltage stress.
3Adaptability or versatility
If the parasitic SCR structure is present in the low-side driver, then the circuit can provide high-side and low-side operations, but it becomes susceptible to latch-up effects during power down mode
Solution Approach 1:
The patent changes the critical parameter of the parasitic SCR structure by elevating its breakdown voltage through the parasitic bipolar structure. This parameter change ensures that the holding voltage of the parasitic SCR remains below the elevated breakdown voltage, creating a voltage window where the SCR cannot latch up. The modified parameter relationships prevent latch-up effects while preserving the high-side and low-side operational capabilities of the driver circuit.
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 protects the driver circuits from high voltage ramps, preventing latch-up conditions and excessive current conduction, ensuring reliable operation during power down modes by maintaining a high breakdown voltage and avoiding low resistance modes.
Implementation Method 1
A low-side driver circuit with a parasitic bipolar structure having a high breakdown voltage is designed to suppress latch-up effects of the parasitic silicon-controlled rectifier (SCR) structure
Data Source
AI summary
An interface device includes an NPN structure along a horizontal surface of a p-doped substrate. The NPN structure has a first n-doped region coupled to an output terminal, a p-doped region surrounding the first n-doped region and coupled to the output terminal, and a second n-doped region separated from the first n-doped region by the p-doped region. The interface device also includes a PNP structure along a vertical depth of the p-doped substrate. The PNP structure includes the p-doped region, an n-doped layer under the p-doped region, and the p-doped substrate. Advantageously, the interface device can withstand high voltage swing (both positive and negative), prevent sinking and sourcing large load current, and avoid entering into a low resistance mode during power down operations.