Voltage controlled current path, a voltage clamp, and an electronic component including a voltage clamp

Patent metadata

Field	Value
Publication number	US-2016336931-A1
Application number	US-201514713538-A
Country	US
Kind code	A1
Filing date	May 15, 2015
Priority date	May 15, 2015
Publication date	Nov 17, 2016
Grant date	—

Abstract

According to a first aspect of this disclosure there is provided a voltage controlled current path. The voltage controlled current path comprises a first stage arranged to conduct current once the voltage at an input node of the first stage exceeds a threshold value. The amount of current that passes through the first stage is a function of the voltage at the input node. A second stage is arranged to pass a current that is a function of the current passing through the first stage.

First claim

What is claimed is:

1 . A voltage controlled current path, comprising:
a first stage arranged to conduct current once the voltage at an input node of the first stage exceeds a threshold value, where the amount of current is a function of the voltage at the input node, and a second stage arranged to pass a current as a function of the current through the first stage.

2 . A voltage controlled current path as claimed in claim 1 , where the first stage comprises a first transistor, where one of:
a) the first transistor is a field effect transistor and a source of the transistor is connected to the input node and a gate of the transistor is arranged to receive a first transistor control voltage, and b) the first transistor is a bipolar transistor and an emitter of the transistor is connected to the input node and a base of the transistor is arranged to receive a first transistor control voltage.

3 . A voltage controlled current path as claimed in claim 1 , where the current flowing in the first transistor is amplified by at least one current mirror, and at least one of the at least one current mirrors is connected to a protected node.

4 . A voltage controlled current path as claimed in claim 1 , further comprising an input circuit where a trigger voltage for initiating current flow is modified once current flow has started so as to provide hysteresis.

5 . A voltage controlled current path as claimed in claim 1 , in which one or more of the at least one current mirror comprises a plurality of transistors arranged in parallel, wherein one or more of the transistors can be inhibited from passing current so as to vary a current gain of the current mirror.

6 . A voltage controlled current path as claimed in claim 1 , in which the first stage comprises a plurality of input transistors, each receiving a respective trigger voltage.

7 . A voltage clamp for limiting voltage excursions at a protected node, the voltage clamp comprising:
a voltage controlled current path that includes:
a first stage arranged to conduct current once the voltage at an input node of the first stage exceeds a threshold value, where the amount of current is a function of the voltage at the input node, and
a second stage arranged to pass a current as a function of the current through the first stage, the voltage controlled current path connected to the protected node.

8 . A voltage clamp as claimed in claim 7 , further comprising a signal input node and a non-zero impedance operably connected between the signal input node and the protected node.

9 . A voltage clamp as claimed in claim 7 in which the input node of the first stage and the protected node are directly connected together.

10 . A voltage clamp as claimed in claim 7 in which the input node of the first stage and the protected node are operably connected together by an intervening component.

11 . A voltage clamp as claimed in claim 7 , in which the voltage clamp is arranged to protect the protected node from overvoltage excursions in excess of a first protection voltage.

12 . A voltage clamp as claimed in claim 7 , further including a second current flow path for protecting the protected node from under voltage excursions where the voltage drops more negative than a second protection voltage.

13 . A system, comprising:
an analog to digital converter; and a voltage clamp in combination with the analog to digital converter, the voltage clamp limiting voltage excursions at a protected node and including a voltage controlled current path that includes:
a first stage arranged to conduct current once the voltage at an input node of the first stage exceeds a threshold value, where the amount of current is a function of the voltage at the input node, and
a second stage arranged to pass a current as a function of the current through the first stage, the voltage controlled current path connected to the protected node.

Assignees

• Analog Devices Global

Inventors

• Hummerston Derek J
• Hurrell Christopher Peter

Classifications

• H02H9/04

  responsive to excess voltage (lightning arrestors H01C7/12, H01C8/04, H01G9/18, H01T) · CPC title

• H02H9/041

  using a short-circuiting device · CPC title

• H03K5/08 Primary

  by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding (H03K5/07 takes precedence; comparing one pulse with another H03K5/22; providing a determined threshold for switching H03K17/30) · CPC title

• G05F3/267 Primary

  using both bipolar and field-effect technology · CPC title