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Deep sleep in an rfid tagRelated Patent Categories: Registers, Coded Record SensorsDeep sleep in an rfid tag description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060289641, Deep sleep in an rfid tag. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application is a continuation of U.S. patent application Ser. No. 10/666,226, entitled "DEEP SLEEP IN AN RFID TAG," filed Sep. 17, 2003. The disclosure of the prior application is considered part of (and is incorporated by reference in) the disclosure of this application. BACKGROUND [0002] The present application describes systems and techniques relating to radio frequency identification (RFID) tag design and use, for example, an RFID chip design for use in tag communication and management. [0003] Traditional passive RFID tags frequently include some form of deactivation capability. Such capability can be of use when reading a large number of passive RFID tags in a field. After a particular tag has been read, that tag can be deactivated to prevent the tag from being read again, while the tag remains supplied with power. [0004] Traditional tag deactivation capabilities provide a non-responsive state for the chip in the tag. The non-responsive state can be dependent on supplied power, such as from a reader or a charge storage device built into the tag (e.g., a large capacitor attached in parallel with the chip's voltage rail so that the chip does not lose power when temporarily removed from the RF field). The non-responsive state can be independent of supplied power, such as a state that blocks the input or the output of the chip using an internal clock that doesn't require maintaining normal power levels in the chip (e.g., a series switch activated in response to a "Cloak" logic command). [0005] When the input is blocked using the Cloak technique, the front end of the chip is effectively disconnected such that incoming signals cannot be recognized in the chip, and the chip cannot respond to any commands from a reader. As described in U.S. Pat. No. 5,963,144, a series switch can be activated to disconnect an antenna of a passive RFID tag for a period determined by a charged resistor-capacitor (RC) circuit. When the output is blocked using the "Mute" technique, the chip continues listening and responding to commands from a reader, but cannot communicate the responses due to the blocked output. As described in U.S. Patent Application Publication No. 2002/0097143 A1, an AND gate can be used to couple a Cloak bar node and an Output node such that no signal can be backscattered from the passive RFID tag when the tag is Muted. SUMMARY [0006] The present disclosure includes systems and techniques relating to radio frequency identification tags including a non-responsive state, which is independent of supplied power, initiated in conjunction with a tag communications reset. According to an aspect, a passive radio frequency identification tag includes an antenna, a radio frequency interface coupled with the antenna, and control logic that initiates a deep sleep state in response an event, the deep sleep state including a non-responsive state that is independent of supplied power, and the control logic providing a following state entered upon conclusion of the non-responsive state, where communications initiate from the following state. [0007] Using the systems and techniques described, passive RFID tags can be placed in a deactivated state of deep sleep, where the tag remains in deep sleep even if it falls out of, and then re-enters the RF field supplying the tag with power. The deep sleep state prevents the tag from timing out of its deactivated state and unexpectedly jumping into the middle of current tag-reader communications. This provides significant flexibility and control in designing RFID chip communication and management protocols. [0008] Moreover, the tag may allow the deep sleep state to be concluded by a command received from a reader, providing additional flexibility. In reader systems designed to read many tags quickly, the deep sleep state may prevent a tag from being read multiple times unnecessarily. Reducing repetitive reading of tags may significantly increase a reader system's efficiency. Moreover, the present systems and techniques may result in reduced tag manufacturing costs. [0009] Details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages may be apparent from the description and drawings, and from the claims. DRAWING DESCRIPTIONS [0010] FIG. 1 illustrates, in block diagram form, a passive RFID tag that employs a deep sleep state. [0011] FIG. 2 illustrates, in block diagram form, a HF tag reader system and multiple HF passive RFID tags employing a deep sleep capability. [0012] FIG. 3 is a state diagram illustrating modes of operation, including a deep sleep mode, as can be implemented in control logic of a passive RFID tag. [0013] FIG. 4 is a state diagram illustrating additional modes of operation, including a deep sleep mode, as can be implemented in control logic of a passive RFID tag. [0014] FIG. 5 is a state diagram illustrating a variation of the modes of operation illustrated in FIG. 4. [0015] FIG. 6 is a state diagram illustrating another variation of the modes of operation illustrated in FIG. 4. [0016] FIG. 7 is a circuit diagram illustrating an example circuit that can be used in implementing a deep sleep mode in a passive RFID tag. [0017] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages may be apparent from the description and drawings, and from the claims. DETAILED DESCRIPTION [0018] FIG. 1 illustrates, in block diagram form, a passive RFID tag 100 that employs a deep sleep state. The tag 100 can include an antenna 110, a radio frequency (RF) interface 120, and control logic 130. The tag 100 can also include a memory 140. [0019] The tag 100 can obtain its power from an inductive coupling of the tag to energy circulating around a reader coil when designed to operate in a low frequency (LF) band (e.g., 13.56 MHz). Alternatively, the tag 100 can use radiative coupling, such as in ultra-high frequency (UHF) and microwave RFID systems. Continue reading about Deep sleep in an rfid tag... Full patent description for Deep sleep in an rfid tag Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Deep sleep in an rfid tag patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. 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