Open-Drain Bus Driver Gate Control for LIN Rise/Fall Timing
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Solution Overview
Problem
Electrical drivers, such as LIN drivers, face challenges in adhering to specified rise and fall times, avoiding damage from short circuit conditions, and requiring insensitivity to process, temperature, and voltage supply variations while operating over a wide voltage range.
Innovation Solution
The electrical driver design incorporates an open drain output transistor, a capacitor, and current sources configured to control the gate voltage of the transistor, ensuring controlled rise and fall times and current limiting, with a current mirror configuration to manage drain-to-source current and a controller to manage switching states based on capacitor voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rise and fall times of the LIN driver output signal are made fast, then the transmission speed is improved, but radio frequency emissions become unacceptably high
Solution Approach 1:
The patent applies dynamics by making the gate voltage application dynamic through a two-stage process: initially applying gate voltage rapidly to achieve fast rise/fall times for meeting transmission speed requirements, then dynamically reducing the gate voltage after the transition is complete to suppress radio frequency emissions. This temporal dynamic control resolves the contradiction between speed and electromagnetic compatibility.
2Object-generated harmful factors
If the rise and fall times of the LIN driver output signal are made slow, then radio frequency emissions are reduced, but duty cycle requirements become difficult to comply with and switching losses increase
Solution Approach 1:
The patent uses dynamic control to apply gate voltage only during the necessary transition period to meet duty cycle requirements, then rapidly removes it to minimize radio frequency emissions. This dynamic on/off gating ensures productivity compliance while suppressing harmful emissions during steady states.
Solution Approach 2:
The patent rushes through the critical transition period by applying sufficient gate voltage quickly to achieve the required signal transition, then immediately stops applying gate voltage. This rushing through the necessary transition while minimizing exposure time resolves the contradiction between meeting duty cycle requirements and reducing radio frequency emissions.
3Adaptability or versatility
If the driver operates over a wide voltage supply range, then adaptability is improved, but sensitivity to voltage supply variations increases
Solution Approach 1:
The patent changes the operating parameter of gate voltage dynamically based on the supply voltage level. By adjusting the gate voltage magnitude and duration according to the actual supply voltage, the driver maintains reliable operation across a wide voltage range while compensating for voltage variations, thus resolving the contradiction between adaptability and reliability.
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 controls rise and fall times, prevents driver damage from short circuits, and ensures operation across a wide voltage range with reduced sensitivity to process, temperature, and supply voltage variations, meeting LIN driver specifications.
Implementation Method 1
a capacitor, C, coupled to a gate of the open drain output transistor
Implementation Method 2
a first current source, I1, coupled to the capacitor through a first transistor, M2
Data Source
AI summary
A driver includes an open drain output transistor, a capacitor, a first current source, and first and second transistors. Upon assertion of a transmit signal to turn on the first transistor, a controller asserts a second control signal to turn on the second transistor responsive to a voltage of the capacitor being less than a threshold voltage of the open drain output transistor to thereby increase the control terminal voltage for the open drain output transistor at a first time rate. The controller deasserts the second control signal to turn off the second transistor responsive to the capacitor voltage exceeding the threshold voltage. Responsive to the capacitor's voltage exceeding the threshold, the first current source charges the capacitor to further increase the control terminal voltage at a second time rate that is smaller than the first time rate.