Electrical connectors – Having circuit interrupting provision effected by mating or...
Reexamination Certificate
2002-11-08
2003-11-18
Prasad, Chandrika (Department: 2839)
Electrical connectors
Having circuit interrupting provision effected by mating or...
C710S303000
Reexamination Certificate
active
06648661
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to electrostatic discharge events in portable electronic devices, and more specifically, to improved electrostatic discharge countermeasure for docking cradles having exposed pins that connect to an active USB interface.
BACKGROUND
Portable electronic devices such as digital cameras, laptop computers, handheld personal digital assistants (PDA's), and the like, are often sold with docking stations or docking cradles. These docking devices are generally connected to a host device, usually a personal computer. Often, the host device and the docking device are connected by common interface cables and protocols, such as a Universal Serial Bus (USB) interface. In order to maintain portability and ease of use, the device to be docked (i.e.,. camera) must interface with an input-output connector on the docking cradle. The nature of the docking cradle input-output connector is often such that the pins are exposed to electrostatic discharge (ESD) events.
When an ESD event occurs on an input-output pin that is connected to a personal computer, the ESD voltage discharge can propagate through the docking cradle to the personal computer. ESD events can result in data loss, unwanted personal computer user intervention, and sometimes physical damage of the personal computer's internal electronic hardware.
The ESD event frequently poses its primary risk when there is no device in the docking station. That is, after the dockable device is inserted into a docking station, the input-output pins are no longer exposed, and no further direct threat exists.
There are many examples of conventional methods that prevent unwanted ESD discharge to this type of docking station device. Other methods of protecting a product from high levels of ESD may require the addition of additional ESD suppression components such as diodes, Zener diodes, resistors and capacitors. These components are sometimes costly, and they are subject to failure after being exposed to a large number of cycles. The number of cycles before failure is also a function of the applied voltage and resulting current. Also, the addition of typical ESD suppression devices may have the highly undesirable effect of decreasing the quality of the USB signal.
U.S. Pat. No. 6,089,879 discloses a “dual-in-line Universal Serial Bus (USB) connector including a plurality of USB ports, a plurality of signal pins associated with the ports, and a pair of mounting tabs. The USB connector is adapted for a circuit board including a first footprint for the dual-in-line USB connector situated at a predetermined location of the circuit board. Also, a second footprint is situated at a predetermined location of the circuit board for receipt of a different type of connector instead of the USB connector.”
U.S. Pat. No. 6,178,514 discloses “an apparatus and method for interfacing a bus to a device. The bus includes a power line carrying power and a signal line carrying a signal. The device including a power input and a signal input. The interface includes a power output connected to the device power input; a power input connected to the bus power line; a signal input connected to the bus signal line; a signal output connected to the device signal input; an energy storage device having an input and an output, the energy storage device output connected to the interface apparatus power output; and a power converter having a power input connected to the interface apparatus power input and a power output connected to the energy storage device input, whereby the power converter receives power from the bus power line and converts it to a form suitable for charging the energy storage device. The power converter further includes a current sensor and a current limiter. The current sensor is connected in series with the power converter power input and output and has an output carrying a signal representative of the current flowing through the current sensor. The current limiter has a predetermined current limit and is operably connected to the power converter power input and power output. The current limiter also has an input connected to the current sensor output for receiving the current sensor signal representative of the current flowing through the current sensor, whereby the current limiter limits the current drawn by the device and the interface apparatus to the predetermined current limit. The interface also includes a signal conditioner that has a first input connected to the energy storage device output, a second input connected to interface apparatus signal input or the interface apparatus signal output, and an output connected to the interface apparatus signal output. The signal conditioner includes a transfer function that produces a signal conditioner output signal at the signal conditioner output. This transfer function is a function of the level of energy in the energy storage device and the level of energy of the bus signal or the signal conditioner output signal.”
U.S. Pat. No. 6,205,505 discloses a “universal serial bus (USB) transmission system for transmitting a monitor control signal and a data signal from a monitor system to a main frame is provided. The universal serial bus transmission system separately includes a universal serial bus interface IC and a monitor controller IC between which the monitor control signal and the data signal are transmitted through a low-speed transmission interface, thereby reducing costs for handling electromagnetic interference (EMI). Furthermore, the universal serial bus interface can be modularized to allow the monitor system to serve as a general monitor system or a USB monitor system, thereby increasing the utility of the monitor system.”
U.S. Pat. No. 6,210,216 discloses that a “USB (Universal Serial Bus) cable includes a cable having an end to which a connection device is attached. The connection device includes an insulative casing in which two USB connectors are fixed and electrically connected to the cable. Two bores are defined in a front wall of the casing for rotatably retaining two bolts. A conductive plate associated with each bolt is fixed in the casing having a first section defining a hole through which the bolt extends and a second section resiliently engaging with a conductive shield of the corresponding USB connector. The first section has step-like edges fixedly received in L-shaped slits defined in the front wall with the first section overlapping an outside surface of the front wall whereby when the connection device is secured to an external grounding panel by the bolts, the conductive plate engages with the grounding panel forming an electrical connection between the shield of the corresponding USB connector and the grounding panel.”
U.S. Pat. No. 6,241,537 discloses “a handheld computer including electrostatic discharge feature. The electrostatic discharge feature is configured on the connector of the handheld computer to dissipate an electrostatic charge having a voltage exceeding a threshold level upon the connector being made with another connector of an accessory device. Examples of an accessory device include communication cradles for use with handheld computers. U.S. Pat. No. 6,241,537 also discloses that “embodiments of the invention provide a versatile connector with a current path to dissipate charge delivered by an ESD event. This feature includes potential damage from ESD events particularly during and connection and deconnection to an accessory device. Further, embodiments of the invention improve reliability in making and maintaining an electrical connection between the handheld computer and accessory device. Additionally, the current associated with an ESD event and its derivative are reduced, minimizing damage such as latchups, register erasure, data loss and physical damage.”
U.S. Pat. No. 6,315,609 discloses an “improved structure universal serial bus (USB) connector female socket in which a grounding ring is disposed at the lower edge of a metal housing enclosing the connector terminals, with the two sides of the me
Byrne Daniel J.
Pandit Amol S.
Robins Mark N.
Hewlett--Packard Development Company, L.P.
Prasad Chandrika
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