Radio frequency data communications device

• US 6,600,428 B1
• Filed: 09/10/1998
• Issued: 07/29/2003
• Est. Priority Date: 05/13/1996
• Status: Expired due to Fees

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Ovard, David K., Tuttle, John R., Rotzoll, Robert R., Tuttle, Mark E., Lowrey, Tyler, Higgins, Brian P., Yu, Shu-Sun, Devereaux, Kevin M., Pax, George E., OʼToole, James E.
• Primary Examiner(s): Holloway, III, Edwin C.
• Application Number:
  US09/151,359
• Time in Patent Office: 1,783 Days
• Field of Search: 340/825.36, 340/10.33, 340/10.34, 340/572.1, 340/5.61, 340/10.41, 323/267, 320/150, 343/741
• US Class Current: 340/10.34
• CPC Class Codes: G06K 19/0707 the arrangement being capable of collecting energy from external energy sources, e.g. thermocouples, vibration, electromagnetic radiation G06K19/0702 takes precedence
• CPC Class Codes: G06K 19/0712 the arrangement being capable of triggering distinct operating modes or functions dependent on the strength of an energy or interrogation field in the proximity of the record carrier active means for hindering electromagnetic reading or writing G06K19/07336
• CPC Class Codes: G06K 19/0716 at least one of the integrated circuit chips comprising a sensor or an interface to a sensor
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07758 arrangements for adhering the record carrier to further objects or living beings, functioning as an identification tag
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10059 transponder driven
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H03L 7/0995 the oscillator comprising a ring oscillator
• CPC Class Codes: H03L 7/148 said digital means comprising a counter or a divider

Abstract

A radio frequency identification device comprises an integrated circuit including a receiver, a transmitter, and a microprocessor. The receiver and transmitter together define an active transponder. The integrated circuit is preferably a monolithic single die integrated circuit including the receiver, the transmitter, and the microprocessor. Because the device includes an active transponder, instead of a transponder which relies on magnetic coupling for power, the device has a much greater range.

Claims

1. A radio frequency identification device comprising:

an integrated circuit including ROM, a processor, a transmitter and a receiver, the ROM, the transmitter and receiver being coupled to the processor, the integrated circuit having a power input terminal configured to be coupled to a battery;

a wake-up circuit configured to periodically activate the receiver, the wake-up circuit being coupled to the receiver and the processor and periodically waking the receiver using a sleep interval derived by the processor from received commands, the wake-up circuit being configured to determine when a valid command is being received and to supply electrical power from the battery to the processor in response thereto;

a power-up circuit configured to provide first and second power-up signals in response to determination of reception of a valid interrogation signal by the wake-up circuit, the first power-up signal being reset by discharging a capacitor via a current mirror, the second power-up signal being later reset when the processor completes a wake-up program stored in ROM including resetting of the wake-up circuit; and

a low battery detection circuit configured to be coupled to the battery and configured to provide a signal indicative of battery voltage having fallen below a predetermined limit in response to the second power-up signal being reset and the battery voltage having fallen below the predetermined limit, the low battery detection circuit having an output coupled to the processor for setting a data bit indicative of battery status responsive to resetting of the second power-up signal.

2. The radio frequency identification device of claim 1 wherein the low battery detection circuit comprises:

a band gap voltage generator configured to generate a predetermined voltage at a reference output;

a voltage divider coupled to the power input terminal and having an output terminal, the voltage divider being configured to provide a scaled voltage representative of battery voltage;

a comparator having first and second inputs and an output, the first input being coupled to the band gap voltage generator reference output, the second input being coupled to the voltage divider output terminal, the comparator being configured to compare the scaled voltage with the predetermined voltage and to generate a low battery signal when the voltage from the battery is less than the predetermined voltage;

a latch having an input coupled to the comparator output and having an output; and

a status register having an input coupled to the latch output, the status register being configured to accept the data bit indicative of low battery status and to supply the data bit indicative of battery status to the processor for formation of a status message to be transmitted in response to a received status request by the receiver.

3. A radio frequency identification device in accordance with claim 1 wherein the integrated circuit responds to commands received by the receiver from an interrogator, wherein the integrated circuit comprises a status register having a value indicating when the low battery detection circuit determines that battery voltage is less than the predetermined voltage and wherein the transmitter transmits the value of the status register in response to a command received by the receiver after setting of the data bit indicative of battery status.

4. A radio frequency identification device in accordance with claim 3 wherein the transmitter selectively transmits the low battery signal using a radio frequency signal responsive to the data bit indicative of battery status.

5. A radio frequency identification device comprising:

an integrated circuit including memory, a processor, a transmitter and a receiver, the memory, the transmitter and receiver being coupled to the processor, the integrated circuit having a power input terminal configured to be coupled to a battery;

a power-up circuit configured to provide a power-up signal in response to determination of reception of a valid interrogation signal, the power-up signal being reset when the processor completes a wake-up program stored in the memory; and

a low battery detection circuit configured to be coupled to the battery and configured to provide a signal indicative of battery voltage having fallen below a predetermined limit in response to the power-up signal being reset, the low battery detection circuit having an output coupled to the processor for setting a data bit indicative of battery status responsive to resetting of the power-up signal.

6. A radio frequency identification device of claim 5, wherein the low battery detection circuit comprises:

a band gap voltage generator configured to generate a predetermined voltage at a reference output;

a voltage divider coupled to the power input terminal and having an output terminal, the voltage divider being configured to provide a scaled voltage representative of battery voltage; and

a comparator having first and second inputs and an output, the first input being coupled to the band gap voltage generator reference output, the second input being coupled to the voltage divider output terminal, the comparator being configured to compare the scaled voltage with the predetermined voltage and to generate a low battery signal when the voltage from the battery is less than the predetermined voltage.

7. A radio frequency identification device of claim 6, further comprising:

a latch having an input coupled to the comparator output and having an output; and

a status register having an input coupled to the latch output, the status register being configured to accept the data bit indicative of low battery status and to supply the data bit indicative of battery status to the processor for formation of a status message to be transmitted in response to a received status request by the receiver.

8. A radio frequency identification device of claim 5, further comprising a wake-up circuit configured to periodically activate the receiver, the wake-up circuit being coupled to the receiver and the processor and periodically waking the receiver using a sleep interval derived by the processor from received commands, the wake-up circuit being configured to determine when a valid command is being received and to supply electrical power from the battery to the processor in response thereto.

9. A radio frequency identification device of claim 5 wherein the integrated circuit responds to commands received by the receiver from an interrogator, wherein the integrated circuit comprises a status register having a value indicating when the low battery detection circuit determines that battery voltage is less than the predetermined voltage and wherein the transmitter transmits the value of the status register in response to a command received by the receiver after setting of the data bit indicative of battery status.

10. A radio frequency identification device in accordance with claim 6 wherein the transmitter selectively transmits the low battery signal using a radio frequency signal responsive to the data bit indicative of battery status.

11. A method of operating a radio frequency device comprising:

coupling an integrated circuit including ROM, a processor, a transmitter and a receiver to a battery, the ROM, the transmitter and receiver being coupled to the processor;

selectively supplying electrical power from the battery to the receiver at predetermined intervals by control signals from a wake-up circuit;

determining, by a wake-up circuit coupled to the processor and receiver, when a valid command is being received and supplying electrical power from the battery to the processor in response thereto;

providing first and second power-up signals from a power-up circuit in response to determination of reception of a valid interrogation signal by the wake-up circuit;

resetting the first power-up signal by discharging a capacitor via a current mirror;

second resetting the second power-up signal when the processor completes a wake-up program stored in ROM including resetting of the wakeup circuit; and

providing a signal from a low battery detection circuit indicative of battery voltage having fallen below a predetermined limit in response to second resetting, the low battery detection circuit having an output coupled to the processor for setting a data bit indicative of battery status responsive to resetting of the second power-up signal.

12. A method of operating a radio frequency device in accordance with claim 11, further comprising periodically waking the receiver using a sleep interval derived by the processor from received commands.

13. A method of operating a radio frequency device in accordance with claim 11, further comprising:

generating a predetermined voltage at a reference output by a band gap voltage generator;

providing a scaled voltage representative of battery voltage;

comparing the scaled voltage with the predetermined voltage and to generate a low battery signal when the voltage from the battery is less than the predetermined voltage; and

supplying the data bit indicative of battery status from the latch to the processor for formation of a status message to be transmitted in response to a received status request by the receiver.

14. A method of operating a radio frequency device in accordance with claim 11 wherein the integrated circuit responds to commands received by the receiver from an interrogator, wherein the integrated circuit comprises a status register having a value indicating when the low battery detection circuit determines that battery voltage is less than the predetermined voltage and further comprising transmitting, by the transmitter, the value of the data bit in response to a command received by the receiver after setting of the data bit indicative of battery status.

15. A method of operating a radio frequency device in accordance with claim 11 further comprising selectively transmitting, by the transmitter, the value of the data bit using a radio frequency signal.

16. A method of operating a radio frequency device comprising:

coupling an integrated circuit including memory, a processor, a transmitter and a receiver to a battery, the memory, the transmitter and receiver being coupled to the processor;

selectively supplying electrical power from the battery to the receiver at predetermined intervals by control signals from a wake-up circuit coupled to the receiver and the processor;

determining, by the wake-up circuit, when a valid command is being received and supplying electrical power from the battery to the processor in response thereto;

providing a power-up signal from a power-up circuit in response to determination of reception of a valid interrogation signal by the wake-up circuit;

resetting the power-up signal when the processor completes a wake-up program stored in memory including resetting of the wake-up circuit; and

providing a signal from a low battery detection circuit indicative of battery voltage having fallen below a predetermined limit in response to resetting, the low battery detection circuit having an output coupled to the processor for setting a data bit indicative of battery status responsive to resetting of the second power-up signal.

17. A method of operating a radio frequency device in accordance with claim 16, further comprising:

providing a predetermined voltage at a reference output of a band gap voltage generator;

providing a scaled voltage representative of battery voltage;

comparing the scaled voltage with the predetermined voltage and to generate a low battery signal when the voltage from the battery is less than the predetermined voltage; and

supplying the low battery signal to the processor.

18. A method of operating a radio frequency device in accordance with claim 16, further comprising:

latching the data bit in a latch having an input coupled to the comparator output and having an output;

accepting the data bit from the latch output in a status register, the status register being configured to accept the data bit; and

supplying the data bit indicative of battery status to the processor for formation of a status message to be transmitted in response to a received status request by the receiver.

19. A method of operating a radio frequency device in accordance with claim 16, further comprising:

periodically activating the receiver by a wake-up circuit using a sleep interval derived by the processor from received commands;

determining when a valid command is being received by the wake-up circuit; and

supplying electrical power from the battery to the processor in response thereto.

20. A method of operating a radio frequency device in accordance with claim 16, wherein the integrated circuit responds to commands received by the receiver from an interrogator, wherein the integrated circuit comprises a status register having a value indicating when the signal from the low battery detection circuit indicates that battery voltage is less than the predetermined voltage;

and

transmitting, by the transmitter, a signal indicating the value of the status register in response to a command received by the receiver after setting of the data bit indicative of battery status.

21. A method of operating a radio frequency device in accordance with claim 17, further comprising selectively transmitting the low battery signal using a radio frequency signal responsive to the data bit indicative of battery status.