LDMOS Switch Circuit Gate Voltage Control
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Solution Overview
Problem
The existing LDMOS devices used in switch circuits within integrated circuits face challenges in controlling the gate voltage due to their asymmetric source and drain formation, making it difficult to manage high drain-source voltages and low operation region voltages, especially when used as floating switches.
Innovation Solution
A switch circuit design that utilizes LDMOS devices with current sources and resistances to control the gate-source voltage (VGS), incorporating N-type and P-type LDMOS configurations, where the gates and sources of the LDMOS devices are connected in a specific manner to adjust the gate-source voltage, allowing for on/off operations between terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LDMOS devices are used in switch circuits within integrated circuits, then high breakdown voltage and fast switching speed are achieved, but gate voltage control becomes difficult due to asymmetric source and drain formation
Solution Approach 1:
The patent introduces a control circuit as an intermediary between the gate terminal and the LDMOS device gate. This control circuit includes a capacitor connected between the gate and source, and a resistor connected between the gate and drain, which together form a voltage divider network that mediates the gate voltage control, making it easier to manage the high breakdown voltage and low operation region voltage requirements
Solution Approach 2:
The patent changes the electrical parameters by introducing external resistors and capacitors that modify the gate-source voltage (VGS) and gate-drain voltage (VGD) relationships. By adjusting these external components, the effective gate control voltage can be tuned to achieve proper switching behavior while maintaining the inherent high breakdown voltage capability of the LDMOS structure
2Adaptability or versatility
If LDMOS devices are used as floating switches to adjust input/output gain, then power supply adjustment is enabled, but asymmetric source and drain formation makes gate control difficult
Solution Approach 1:
The control circuit acts as a mediator that enables versatile power supply adjustment through floating switch configurations while simplifying gate control. The capacitor and resistor network in the control circuit provides the necessary voltage division and timing control to manage multiple floating switches at different power supply voltages
Solution Approach 2:
The control circuit design provides multi-functionality by enabling both gain adjustment and power supply voltage adjustment through the same floating switch mechanism. The universal control approach works across different voltage levels and switching configurations, making the system adaptable to various operational requirements
Data Source
AI summary
The present invention relates to a switch circuit, and more particularly, to a switch circuit that uses an LDMOS (lateral diffusion metal oxide semiconductor) device inside an IC (Integrated Circuit). In the switch circuit that uses the LDMOS device according to an embodiment of the present invention, a gate-source voltage (VGS) of the LDMOS device may be stably controlled through a current source and resistances, the characteristics of a switch may be maintained regardless of the voltages of both terminals (A and B) by using an N-type LDMOS and a P-type LDMOS in a complementary manner, and the current generated by the current source is offset inside the switch without flowing to the outside of the switch.