Low voltage and low power frequency synthesizer

• US 4,893,087 A
• Filed: 01/07/1988
• Issued: 01/09/1990
• Est. Priority Date: 01/07/1988
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Davis, Walter L.
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Callahan, Timothy P.
• Application Number:
  US07/141,380
• Time in Patent Office: 733 Days
• Field of Search: 328/14, 328/15, 328/155, 307/271, 307/262, 331/1 A, 331/16, 331/17, 331/18
• US Class Current: 327/106
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H03J 5/0281 the digital values being held in an auxiliary non erasable memory
• 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 7/187 using means for coarse tuning the voltage controlled oscillator of the loop H03L7/191 - H03L7/195 take precedence

Abstract

A low power and low voltage frequency synthesizer includes a memory containing information to provide divisor information to the variable divider of a phase locked loop and information to select predetermined values of capacitance to connect to the frequency determining resonant network of the VCO to provide a coarse tuning. This tuning is then further modified by the normal operation of the phase locked loop.

Claims

1. A low voltage and low power frequency synthesizer including a variable divider phase locked loop for controlling the output frequency of a voltage controlled oscillator (VCO) comprising:

memory means having information corresponding to a desired frequency and divisor information for the phase locked loop and the VCO; and

frequency capacitance switch means coupled between said memory and said VCO responsive to additional information to select a predetermined value of capacitance, said switch means including a plurality of capacitors from which the frequency capacitance switch means may select, said switch means further including means producing a course tuning frequency determining network of the VCO whereby a broad range of frequencies can be synthesized at lower voltages and maintained with lower power consumption with the phase locked loop operating to maintain the precision of the desired frequency.

2. The frequency synthesizer of claim 1, wherein the memory means further comprises a programmable Read Only Memory (ROM).

3. The frequency synthesizer of claim 2, wherein said ROM is electrically erasable.

4. The frequency synthesizer of claim 1, wherein the plurality of capacitance includes at least five values in a binary related sequence.