Trimmable circuitry for providing compensation for the temperature coefficients of a voltage controlled crystal-less oscillator

• US 5,963,105 A
• Filed: 07/31/1997
• Issued: 10/05/1999
• Est. Priority Date: 07/31/1997
• Status: Expired due to Term

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Dallas Semiconductor Corporation (Analog Devices, Inc.)
• Inventors: Nguyen, Cong Dinh
• Primary Examiner(s): KINKEAD, ARNOLD M
• Application Number:
  US08/903,822
• Time in Patent Office: 796 Days
• Field of Search: 331/176, 331/185, 331/186, 331/177 R, 331/1 R, 331/175, 331/17, 331/143
• US Class Current: 331/176
• CPC Class Codes: H03L 1/022 by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature H03L1/021 takes precedence
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation

Abstract

In an integrated crystal-less device that generates an output signal with the frequency of the output signal dependent at least in part on a resistive element, there is provided circuitry for providing compensation for the temperature coefficient the of resistive element, the circuitry includes a bandgap reference and a resistive network. The bandgap reference utilizes components having stable temperature coefficient to generate a first voltage, a reference voltage, and also to generate second voltage, a voltage proportional to absolute temperature. The resistive network includes two trimmable resistors, which are trimmed such that the resistive network in combination with the bandgap reference compensates for the absolute value of the resistive element in a selected temperature range.

Claims

1. In a monolithic crystal-less oscillator device, circuitry for providing compensation for the temperature dependency of at least a resistive element of the crystal-less oscillator device, said circuitry comprising:

a voltage reference generator connected to a base of a first transistor of the monolithic crystal-less oscillator, said voltage reference generator for generating a first voltage with a stable temperature coefficient and a second voltage with a stable temperature coefficient; and

a resistor network coupled between the base and an emitter of the first transistor of the monolithic crystal-less oscillator, said resistor network including a plurality of resistors, said plurality of resistors including a first resistor connected to the emitter of the first transistor, and further including a second resistor connected to said first resistor with said first resistor and said second resistor generally coupled in parallel with a frequency-controlled resistor of the monolithic crystal-less oscillator.

2. The circuitry as recited in claim 1, wherein said first resistor is trimmable.

3. The circuitry as recited in claim 2, wherein said plurality of resistors includes a third resistor connected to the base of the first transistor.

4. The circuitry as recited in claim 3, and wherein said plurality of resistors includes a fourth resistor connected to said third resistor and between said first trimmable resistor and said second resistor, said fourth resistor being trimmable.

5. The circuitry as recited in claim 4, wherein said plurality of resistors includes a fifth resistor connected to said third resistor and said fourth resistor.

6. A device for providing compensation for the temperature dependency of a crystal-less oscillator circuitry, said device comprising:

a first resistor coupled to an emitter of a first transistor of the crystal-less oscillator circuitry; and

a second resistor coupled to said first resistor, with said first resistor and said second resistor being generally coupled in parallel with a frequency-controlled resistor of the crystal-less oscillator circuitry.

7. The device as recited in claim 6, wherein said first resistor is a variable resistor.

8. The device as recited in claim 6, and further comprising a voltage generator coupled to the base of the first transistor, said voltage generator for generating a reference voltage.

9. The device as recited in claim 6, and further comprising a third resistor coupled to the base of the first transistor.

10. The device as recited in claim 9, and further comprising a fourth resistor coupled to said third resistor and between said first resistor and said second resistor.

11. The device as recited in claim 10, wherein said fourth resistor is a variable resistor.

12. The device as recited in claim 10, and further comprising a fifth resistor coupled to said third resistor and said fourth resistor.

13. The device as recited in claim 12, and further comprising a voltage generator coupled to the base of the first transistor, said voltage generator for generating a reference voltage.