Electronic digital logic circuitry – Interface – Logic level shifting
Reexamination Certificate
2007-08-21
2007-08-21
Barnie, Rexford (Department: 2819)
Electronic digital logic circuitry
Interface
Logic level shifting
C326S062000, C326S065000, C326S081000, C326S095000, C326S098000, C327S333000
Reexamination Certificate
active
11162638
ABSTRACT:
A bus switch chip is limited to operating with a power-supply voltage of 1.8 volts relative to a 0-volt ground. Differential bus signals switched through the bus switch chip swing from 2.7 to 3.3 volts, well above the chip's specified power-supply voltage. The bus switch chip is level-shifted by applying a 1.5-volt signal as the chip's ground, and a 3.3-volt signal as its power supply, so the chip's net power supply is within the specification at 1.8 volts. High-Definition Multimedia Interface (HDMI) and Digital Visual Interface (DVI) require that the differential signals are never driven to ground. However, some non-compliant video transmitters drive differential signals to ground when disabled. External pullup resistors or internal pullup transistors in the bus switch chip are added to the bus signals from non-compliant transmitters to pull disabled signals above the 1.5-volt chip ground to prevent damage from signals below the chip's 1.5-volt ground.
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Hui Chi-Hung
Li Xianxin
Auvinen Stuart T.
Barnie Rexford
gPatent LLC
Pericom Semiconductor Corp.
White Dylan
LandOfFree
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