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Patent Issued for Bi-Directional Switch Using Series Connected N-Type MOS Devices in Parallel with Series Connected P-Type MOS Devices

May 14, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Aherne, David (Limerick, IE); Dunlea, John O (Limerick, IE), filed on August 23, 2012, was published online on April 29, 2014.

The patent's assignee for patent number 8710541 is Analog Devices, Inc. (Norwood, MA).

News editors obtained the following quote from the background information supplied by the inventors: "Two NDMOS devices can be connected in series with their sources connected to each other and their gates connected to each other to make an NDMOS switch. Two PDMOS devices can also be connected in series with their sources connected to each other and their gates connected to each other to make a PDMOS switch. However, no switches have been formed using a combination of series connected NDMOS and series connected PDMOS devices. The reason why these two types of series connections have not been combined into a single switch is that in a conventional DMOS manufacturing process one of the device types has to have its source tied to the silicon substrate. For example in a P-type silicon substrate every NDMOS device has to have its source connected to the substrate. Similarly, in an N-type silicon substrate every PDMOS device has to have its source connected to the substrate. Therefore, a plurality of processes (e.g., a conventional NDMOS process plus a conventional PDMOS process) would be required in order to form a single switch having both types of series connections--which would be costly and time consuming. Since both types of series connections would not have been used together, a parallel configuration of both types of series connections would also not have been considered feasible or practical.

"A new process has been developed which allows the source of a DMOS device to be at a different potential from the substrate, thereby allowing the series connection of both NDMOS and PDMOS in the same process. Circuits that include both types of series connections, such as the bi-directional switch of the present invention, are therefore possible to manufacture with less expense."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "In one embodiment, a bi-directional switch is formed using a pair of series connected N-type MOS devices connected in parallel with a pair of series connected P-type MOS devices.

"In a second embodiment, the bi-directional switch is a DMOS switch including a pair of series connected NDMOS devices connected in parallel with a pair of series connected PDMOS devices. One advantage of the bi-directional DMOS switch in accordance with the second embodiment is that the switch allows rail-to-rail operation without the need to use a charge pump, e.g., a charge pump to generate the gate voltage for a conventional DMOS switch. To support rail-to-rail operation, the charge pump generates a supply voltage that exceeds the maximum allowed input signal in order to keep the conventional DMOS switch turned on. Disadvantages of using the charge pump in this manner include high supply current and slow switching speed. The DMOS switch of the present invention would avoid these disadvantages."

For additional information on this patent, see: Aherne, David; Dunlea, John O. Bi-Directional Switch Using Series Connected N-Type MOS Devices in Parallel with Series Connected P-Type MOS Devices. U.S. Patent Number 8710541, filed August 23, 2012, and published online on April 29, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=74&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=3677&f=G&l=50&co1=AND&d=PTXT&s1=20140429.PD.&OS=ISD/20140429&RS=ISD/20140429

Keywords for this news article include: Silicon, Analog Devices Inc., Medical Device Companies.

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Source: Journal of Engineering


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