Microchip Technology Inc.

Daniel Butler

Joseph Harry Julicher

Hartono DArmawaskita

David Otten

Reston A Condit

A low power Universal Serial Bus (USB) capable device uses a weak pull-up resistance that is coupled to at least one data line of the USB for detection of when the USB capable device is connected to a USB host or hub. When the USB capable device is not connected to the USB host or hub, USB peripheral, including the USB transceiver, USB voltage regulator, serial interface and/or USB logic circuits required for USB operation may be powered down to conserve power drawn by the USB capable device. When the USB capable device is connected to the USB host or hub, a voltage from the weak pull-up will be significantly reduced, thus signaling that the USB peripheral and associated circuits should be powered up for normal USB operation.

Detecting connection to a USB host or hub without using an extra status input

Clock speed is controlled based upon the supply voltage to a digital device. When the supply voltage is below a reference voltage the clock speed will be slower than if the supply voltage is above the reference voltage. A phase-lock-loop (PLL) may be used to generate a higher frequency that is an integer multiple of a reference oscillator. The clock speed will be proportional to the frequency multiplication of the PLL when the faster clock speed is selected. A multiplexer is used to switch between different frequency sources, and a timer can be used to insure stable operation of the PLL. A status configuration register has status and control bits for indicating and controlling operation of the clock speed control. A universal serial bus (USB) device can operate at a slower clock with reduced operating voltage, and at a faster clock with increased operating voltage.

Digital system having selectable clock speed based upon available supply voltage and PLL configuration register settings

A special test mode is incorporated within a USB transceiver of a digital system, and when the special test mode is activated, USB eye pattern test data signal waveforms, e.g., a continuous stream of USB state transitions (defined by the USB specification) are transmitted on the USB data lines connected to the USB transceiver. Conventional test equipment may be attached to the USB data lines and the signal quality monitored. Circuit changes can be made to the digital system and the results easily measured. When the USB eye pattern test data signal waveforms on the USB data lines of the digital system are of satisfactory quality, the special test mode may be turned off and the USB transceiver will resume operation as a normal USB device.

Growing community of inventors

Chandler, AZ, United States of America

Daniel Butler