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Layout for the Motherboard USB Voltage Regulator Over-Current Protection Circuit

IP.com Disclosure Number: IPCOM000099068D
Publication Date: 2005-Mar-10
Document File: 3 page(s) / 131K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a new layout for the USB voltage over-current protection circuit. Benefits include saving space on motherboards which support USB front panels.

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Layout for the Motherboard USB Voltage Regulator Over-Current Protection Circuit

Disclosed is a method for a new layout for the USB voltage over-current protection circuit. Benefits include saving space on motherboards which support USB front panels.

Background

For motherboards with a USB front panel, an on-board voltage regulator must be in place to supply power to the USB devices plugged into the USB front panel daughter card. This voltage regulator provides over-current protection for the system; however, the over-current limiting mechanism should allow a means for resetting it without manual user intervention. Polymeric PTCs and solid-state switches are normally used for over-current limiting.

Also for over-current protection purposes, the USB front panel daughter card may have its own thermistor, depending on the vendor’s implementation. If it does not have one, then the motherboard needs to have an over-current limiting mechanism (normally a thermistor).

General Description

The disclosed method uses a dual footprint layout for the USB voltage over-current protection circuit (see Figure 1). The disclosed method uses an 1812 case size thermistor and two 1206 case size 0ohm resistors. The two 1206 case-size resistors are used instead of 0805 resistors to avoid a “tombstone” or shift skew defect during high volume manufacturing (HVM). Figure 2 shows the “tombstone” defect. The pad of a 0805 case size is too small, compared to the pad of a 1812 case size (i.e. the...