Voltage sampling switch and method therefor

摘要

A voltage switch for handling negative voltages includes an input terminal coupled to a voltage that is greater than a voltage rating of oxide in the voltage switch, a top capacitor plate pre-charge module including three cascoded p-channel transistors coupled between a supply voltage and a top plate of a capacitor, a bottom capacitor plate pre-charge module including two cascoded n-channel transistors coupled between a bottom plate of the capacitor and ground, and an output voltage module including an output terminal and four cascoded n-channel transistors with control electrodes of a first and fourth of the cascoded n-channel transistors coupled to a boost node. Control electrodes of a second and third of the cascoded n-channel transistors coupled to the top plate of the capacitor. A voltage switch for positive voltages is also disclosed.

主权项

1. An input voltage sampling switch, comprising:
an input voltage terminal for receiving an input voltage, wherein the input voltage is higher than a voltage rating for at least some transistors in the input voltage sampling switch; a first capacitor including a top plate and a bottom plate; a top capacitor plate pre-charging circuit including three cascoded transistors,
a first of the three cascoded transistors includes a source electrode coupled to a supply voltage,a second of the three cascoded transistors is coupled between the first and third of the three cascoded transistors and a control electrode of the second of the three cascoded transistors is coupled to the bottom plate of the first capacitor, anda third of the three cascoded transistors includes a source electrode coupled to the top plate of the first capacitor; a first node located between the top plate of the first capacitor and the source electrode of the third of the three cascoded transistors; an output switch; and an output voltage terminal coupled to the input voltage terminal through an output switch, wherein operation of the output switch is controlled in part by an output of the top capacitor plate pre-charging circuit at the first node.