Power supply for universal serial bus interface with programmable bus pullup resistor
Patent No. US6996727 (titled "Power supply for universal serial bus interface with programmable bus pullup resistor") on Aug 28, 2000. The application was issued on Feb 7, 2006.
What is this patent about?
'727 is related to the field of power supplies, specifically those used in Universal Serial Bus (USB) interfaces. The background involves providing a stable 3.3V supply to the USB I/O, but conventional designs lack a low-power standby mode, leading to unnecessary current draw when the USB device is idle.
The underlying idea behind '727 is to implement a two-state power supply for USB interfaces. In a normal operating mode, a primary power supply provides the necessary voltage. However, when a low-power mode is desired, this primary supply is shut down, and a secondary, programmable resistor takes over the task of maintaining the bus pull-up, significantly reducing overall current consumption.
The claims of '727 focus on an apparatus with a power supply that generates either a standard voltage level or a power-down voltage level. Crucially, when in the power-down mode, a programmable resistor pulls up a bus pull-up resistor located on a bus external to the power supply. This programmable resistor is controlled by a register that is loaded from a non-volatile memory.
In practice, the non-volatile memory stores trim bits that are loaded into the register. These bits control the resistance of the programmable resistor. This allows the circuit to compensate for process variations in the external bus pull-up resistor, ensuring proper bus operation even when the primary power supply is off. The power supply and programmable resistor are controlled by a power down signal.
This design differentiates itself from prior approaches by introducing a power-down mode where the primary power supply is disabled, and a programmable resistor maintains the bus pull-up. This significantly reduces current consumption compared to traditional designs that keep the primary power supply active even when the USB device is in a standby state. The programmability also allows for compensation of manufacturing variations, improving reliability.
How does this patent fit in bigger picture?
Technical Landscape
In the early 2000s when '727 was filed, at a time when USB interfaces were becoming increasingly prevalent, power management in electronic devices was typically implemented using discrete components or relatively simple linear regulators. When systems commonly relied on external power supplies or basic voltage regulation circuits rather than highly integrated power management solutions, achieving low power consumption in standby mode was non-trivial due to the limitations of available components and control techniques.
Prosecution Position
The disclosed invention provides a power supply architecture that can selectively generate a standard voltage level or a power-down voltage level to reduce current consumption. This architectural shift enables a USB interface to operate with a regulated supply voltage in a standard mode and significantly reduce power consumption in a power-down mode. The technical effect is an on-chip USB power supply with a power-down mode that achieves reduced current consumption, potentially compensating for process variations.
Claims
This patent contains 19 claims, of which claims 1, 17, 18, and 19 are independent. The independent claims generally focus on a power supply apparatus and method for reducing current consumption by using a programmable resistor to pull up a bus pullup resistor when in a power down mode. The dependent claims generally elaborate on specific implementations and features of the power supply, such as the type of interface powered, the use of an indication signal, and the configuration of the programmable resistor.
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US6996727
- Application Number
- US09649551A
- Filing Date
- Aug 28, 2000
- Publication Date
- Feb 7, 2006
- External Links
- Slate, USPTO, Google Patents