PLL circuit used temperature compensated VCO

• US 6,342,798 B1
• Filed: 12/30/1999
• Issued: 01/29/2002
• Est. Priority Date: 01/06/1999
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Yoshida, Toshiro
• Primary Examiner(s): Lam, Tuan T.
• Assistant Examiner(s): NGUYEN, LINH M
• Application Number:
  US09/476,231
• Time in Patent Office: 761 Days
• Field of Search: 327/146, 327/147, 327/155, 327/156, 327/512, 327/513, 331/25, 331/176
• US Class Current: 327/156
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence
• CPC Class Codes: H03L 2207/06 Phase locked loops with a controlled oscillator having at least two frequency control terminals
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop
• CPC Class Codes: H03L 7/104 using an additional signal from outside the loop for setting or controlling a parameter in the loop H03L7/107, H03L7/12 take precedence

Abstract

A phase locked loop (PLL) circuit used a temperature compensated voltage controlled oscillator (VCO), in which phases and frequencies of the VCO are synchronized with inputted data and the VCO is always controlled to oscillates within a pull in rage of a phase comparator, is provided. The PLL circuit used the temperature compensated VCO provides a temperature/voltage converter used a temperature sensor. By giving an external control voltage to the VCO as an input voltage, the VCO is controlled to oscillate within the pull in range of the phase comparator. With this, a stable PLL operation can be always performed even when an ambient temperature changes.

Claims

1. A phase-locked loop (PLL) circuit including a temperature compensated voltage controlled oscillator (VCO), in which phases and frequencies of the VCO are synchronized with inputted data, comprising:

a phase comparator for detecting phase shifts of said inputted data and of signals outputted from said VCO from optimal signals, and for outputting control signals based on the detected results;

a signal filter for smoothing said control signals and outputting said smoothed signals to said VCO; and

a temperature/voltage converter for outputting beforehand to said VCO external control voltages, with which said VCO oscillates within a pull-in range of said phase comparator, wherein said external control voltages are varied independently from said control signals based on the detected results in the phase comparator.

2. A PLL circuit including a temperature compensated VCO in accordance with claim 1, wherein said temperature/voltage converter comprises:

a temperature sensor for sensing an ambient temperature;

an analog/digital converter for converting said sensed ambient temperature to a digital signal;

a memory for storing data provided to said VCO as an optimal external control voltage in response to said ambient temperature; and

a digital/analog converter for converting said stored data to an analog signal and outputting said analog signal to said VCO as said optimal external control signal.

3. A PLL circuit including a temperature compensated VCO in accordance with claim 1, wherein:

temperature characteristics of said VCO are measured beforehand.

4. A PLL circuit including a temperature compensated VCO in accordance with claim 3, wherein:

said data to be stored in said memory and provided to said VCO as optimal external control voltages are based on said measured temperature characteristics of said VCO.

5. A PLL circuit including a temperature compensated VCO in accordance with claim 2, wherein:

said data stored in said memory are erasable if necessary.

6. A PLL circuit including a temperature compensated VCO in accordance with claim 2, wherein:

said memory is an electrically erasable programmable read only memory (EEPROM).