Random delay generation for thin-film transistor based circuits

• US 8,810,298 B2
• Filed: 11/24/2009
• Issued: 08/19/2014
• Est. Priority Date: 11/26/2008
• Status: Expired due to Fees

• Current Assignee: Ensurge Micropower ASA
• Original Assignee: Thin Film Electronics ASA
• Inventors: Subramanian, Vivek, Mao, Mingming, Wang, Zhigang
• Primary Examiner(s): Johnson, Ryan
• Application Number:
  US12/625,435
• Publication Number:
  US 20100295661A1
• Time in Patent Office: 1,729 Days
• Field of Search: 327/261, 327/262, 327/263, 327/264, 327/269, 327/270, 327/271, 327/272, 327/276, 327/277, 327/278, 327/28, 331/57, 331/78, 340/10.1
• US Class Current: 327/261
• 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 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: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H03B 5/1203 the amplifier being a single transistor
• CPC Class Codes: H03K 3/0315 Ring oscillators
• CPC Class Codes: H03K 3/033 Monostable circuits
• CPC Class Codes: H03K 3/355 Monostable circuits
• CPC Class Codes: H03K 5/13 Arrangements having a single output and transforming input signals into pulses delivered at desired time intervals
• CPC Class Codes: H03K 5/133 using a chain of active delay devices
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04H 20/16 Arrangements for broadcast or for distribution of identical information repeatedly

Abstract

Circuits and circuit elements configured to generate a random delay, a monostable oscillator, circuits configured to broadcasting repetitive messages wireless systems, and methods for forming such circuits, devices, and systems are disclosed. The present invention advantageously provides relatively low cost delay generating circuitry based on TFT technology in wireless electronics applications, particularly in RFID applications. Such novel, technically simplified, low cost TFT-based delay generating circuitry enables novel wireless circuits, devices and systems, and methods for producing such circuits, devices and systems.

Claims

1. A circuit configured to generate a delay comprising:

a) a delay element having an input terminal and an output terminal, the delay element comprising one or more inverters;

b) a capacitor having a first terminal receiving an input and a second terminal coupled to said input of said delay element; and

c) a thin-film field-effect transistor (TFT) having a first source/drain terminal receiving a DC source or supply voltage, a second source/drain terminal receiving said input of said delay element, and a gate electrically connected to said second source/drain terminal, said TFT being configured to provide a current and/or voltage to said capacitor,

wherein said current and/or voltage has a value that falls randomly within a predetermined range.

2. The circuit of claim 1, wherein said TFT comprises a material providing said predetermined range of current and/or voltage.

3. The circuit of claim 2, wherein said material comprises amorphous silicon or polysilicon doped with an amount of dopant sufficient to control a threshold voltage of said TFT and provide said predetermined current and/or voltage range.

4. The circuit of claim 1, wherein said TFT has a geometry providing said predetermined range.

5. The circuit of claim 1, wherein said delay element comprises a plurality of inverting logic gates.

6. The circuit of claim 1, wherein said one or more inverters comprises an inverter having (i) an input coupled to the capacitor and to an output of the TFT, and (ii) an output comprising a timing signal.

7. A monostable oscillator, comprising the circuit of claim 1, and a feedback path from the output terminal of the delay element to an input of the circuit.

8. The monostable oscillator of claim 7, further comprising a feedback path from the output terminal of the delay element to an input of the circuit.

9. The monostable oscillator of claim 7, wherein said predetermined range corresponds to an operating current and/or voltage range of a TFT.

10. The monostable oscillator of claim 7, wherein said value of said current and/or voltage is related to one or more variations in a manufacturing process of said TFT.

11. The monostable oscillator of claim 7, wherein said TFT comprises a channel material comprising an amorphous semiconducting material, a crystalline semiconducting material, or combinations thereof.

12. The monostable oscillator of claim 7, wherein said feedback path comprises inverter logic having an input coupled to a first electrode of the capacitor and an output comprising a timing signal.

13. A circuit configured to broadcast a repetitive message in a wireless system, comprising:

a) an antenna configured to receive a power transmission and broadcast a repetitive message;

b) a power-up circuit providing an initiation signal;

c) the monostable oscillator of claim 7, configured to provide a repeating timing signal;

d) a memory element providing said message; and

e) an output circuit configured to broadcast said message in response to said timing signal.

14. The circuit of claim 13, further comprising:

a) one or more shift register(s); and

b) a clock generator configured to provide a clock signal to said one or more shift registers.

15. The circuit of claim 13, wherein a period of said repeating timing signal corresponds to an RC time constant of said TFT and said capacitor.

16. The circuit of claim 13, wherein said repetitive message comprises a repetitive identification message.

17. A wireless system comprising at least two wireless devices, each wireless device comprising:

a) an antenna configured to receive a power transmission and broadcast a repetitive identification message;

b) a power converting element coupled to said antenna; and

c) the circuit of claim 13, configured to generate said repetitive identification message.

18. The system of claim 17, wherein said repeating timing signal has a period corresponding to a value of a characteristic electrical parameter of said TFT.

19. The system of claim 18, wherein said characteristic electrical parameter comprises a leakage current, an on-current, or a threshold voltage.

20. The system of claim 17, wherein said value of said current and/or voltage is related to one or more variations in a manufacturing process of said TFT.

21. The system of claim 17, wherein said wireless system comprises an RFID system.

22. The system of claim 17, wherein said wireless devices comprise RFID tags.

23. A method of forming a collision tolerant wireless system, comprising:

a) determining a target variation range in a broadcast delay of the wireless devices of the wireless system of claim 17, the target variation range being configured to reduce a broadcast collision frequency between said wireless devices when said wireless devices broadcast repetitive messages in the same read field;

b) determining a random variation range in the broadcast delay of said wireless devices;

c) comparing said target variation range and said random variation range; and

d) if said random variation range is at least equal to said target variation range, making said wireless devices having said random variation range in their broadcast delay.

24. The method of claim 23, further comprising:

a) determining whether said random variation range can be increased by modifying the manufacturing process when said random variation range is less than said target variation range;

b) when said random variation range can be increased, modifying said manufacturing process; and

c) making said wireless devices using the modified manufacturing process.

25. The method of claim 24, wherein modifying said manufacturing process comprises changing at least one static design parameter, implementing at least one manufacturing change, or a combination thereof.

26. The method of claim 24, wherein said manufacturing process comprises forming at least one part of a thin film transistor (TFT).

27. The method of claim 23, wherein said wireless system comprises an RFID system.

28. The method of claim 23, wherein said wireless devices comprise RFID tags.

29. The method of claim 23, wherein said wireless devices have substantially the same architecture.