Low-Side Switch Gate Discharge Sequencing Against Parasitic Turn-On
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Solution Overview
Problem
Existing low-side switch integrated circuits face a high risk of damage due to parasitic capacitance, which can inadvertently turn on the switch transistor, potentially causing damage to electronic components.
Innovation Solution
A low-side switch circuit with a first and second pull-down branch, activated by complementary and delayed enable signals, along with a clamping and overvoltage protection branch, to manage and discharge the control terminal of the switch transistor, reducing the risk of inadvertent conduction and overvoltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single pull-down branch is used to discharge the control terminal, then the circuit structure is simple, but the discharge speed is insufficient and the transistor may inadvertently turn on
Solution Approach 1:
The single pull-down branch is segmented into two independent pull-down branches (first pull-down branch and second pull-down branch). Each branch can be independently controlled by its own enable signal, allowing staged discharge of the control terminal. This segmentation increases discharge capability and reliability while maintaining reasonable circuit complexity.
Solution Approach 2:
The first pull-down branch is activated earlier than the second pull-down branch through complementary and delayed enable signals. This preliminary action ensures that the control terminal begins discharging before the second branch activates, preventing inadvertent transistor turn-on while managing the overall discharge process in stages.
2Speed
If both pull-down branches are activated simultaneously, then the discharge speed is maximized, but the risk of overvoltage damage increases
Solution Approach 1:
The first pull-down branch activates in advance of the second pull-down branch, creating a staged discharge sequence. This preliminary action allows the control terminal voltage to decrease gradually, avoiding the sudden voltage drop that could cause overvoltage damage while still achieving sufficient discharge speed through the combined effect of both branches.
Solution Approach 2:
The clamping branch is configured to activate before or during the pull-down process to provide beforehand cushioning. When the voltage difference between the output terminal and control terminal exceeds a threshold, the clamping branch conducts to limit the voltage, protecting the transistor from overvoltage damage while the pull-down branches discharge the control terminal.
Data Source
AI summary
The present application discloses a low-side switch circuit and its control method, a low-side switch integrated circuit, and an electronic device. The low-side switch circuit comprises a switch transistor, and a first pull-down branch and a second pull-down branch connected between a control terminal of the switch transistor and ground. The first pull-down branch is configured to be activated or deactivated in response to a first enable signal, and when activated, generate a first pull-down current to discharge the control terminal of the switch transistor. The second pull-down branch is configured to be activated or deactivated in response to a second enable signal, and when activated, generate a second pull-down current to discharge the control terminal of the switch transistor. The first pull-down branch is configured to be activated earlier than the second pull-down branch, or be deactivated later than the second pull-down branch.