Darrell A Davis

US Patent:

59399112, Aug 17, 1999

Filed:

Mar 5, 1998

Appl. No.:

9/033619

Inventors:

Scott Robert Humphreys - Boynton Beach FL
Darrell Eugene Davis - Sunrise FL
Barry W. Herold - Delray Beach FL

Assignee:

Motorola, Inc. - Schaumburg IL

International Classification:

H03L 706

US Classification:

327147

Abstract:

A low input prescaler (800) that is responsive to input signals having low amplitude alternating current (AC) components includes a switched tunable prescaler (280) that generates a prescaler output signal (221) having a prescaler output frequency during an operational state of the prescaler and having a free-running frequency that is responsive to a tuning control signal (216) during a tuning state of the prescaler. A frequency comparator (235) generates a comparator output in response to a difference between a reference frequency and the prescaler output frequency. A prescaler tuner (290, 390) adjusts the tuning control signal in response to the comparator output during the tuning state to minimize the difference between the reference frequency and the prescaler output frequency, and holds the tuning control signal during the operational state. The prescaler is used in phase lock loops (200, 400, 600) and other circuits.

US Patent:

57369046, Apr 7, 1998

Filed:

Dec 2, 1996

Appl. No.:

8/753833

Inventors:

Scott R. Humphreys - Boynton Beach FL
Darrell E. Davis - Sunrise FL

Assignee:

Motorola, Inc. - Schaumburg IL

International Classification:

H03L 708

US Classification:

331 10

Abstract:

A PLL circuit (401), including a VCO (420) having a trimming port (418) and a tuning port (416), a PLL controller (404), a variable voltage source (408), a voltage measuring circuit (426) and a multiplexer (412, 414, 428), performs automatic trimming of the VCO (420). The PLL circuit (401) accomplishes this by initiating a trimming mode that controls the multiplexer so that it couples the output of the PLL controller (404) to the trimming port (418), and the output of the variable voltage source (408) to the tuning port (416), thereby to phase lock the VCO (420) to the reference frequency signal (421). The PLL circuit (401) then measures, by way of the voltage measuring circuit (426), a voltage at the trimming port (418), switches the PLL circuit (401) to an operational mode, and then adjusts the variable voltage source (408) to be substantially equal to the voltage measured.