Over-voltage protection circuit

摘要

An over-voltage protection circuit suitable for use at a front-end of an on-chip analog module such as an analog-to-digital converter (ADC) includes an input potential divider that can be disconnected from the module when the module is idle (or working on any other input such as the ADC sampling another channel causing the current channel to be idle) while still providing protection for front-end devices. A first NMOS transistor pair connects or disconnects the potential divider to or from ground in response to a control signal, and a second transistor pair including a NMOS transistor and a PMOS transistor ensures that the output does not rise above the supply voltage.

主权项

1. An over-voltage protection circuit, comprising:
an input; an output; a potential divider connected to the input; a first switch arrangement connected to the potential divider and having a select input for receiving a first select signal (SELA); a second switch arrangement connected between the potential divider at a first node and the output, and having a control terminal connected to the potential divider and the first switch arrangement at a second node; and a delay circuit connected between the control terminal of the second switch arrangement and the second node, wherein in a first mode of operation, the first switch arrangement enables the potential divider in response to receipt of the first select signal and closes the second switch arrangement, such that a voltage at the first node is transferred to the output at a third node, and in a second mode of operation, in response to the first select signal, disables the potential divider.