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Serially Programmable Crystal Oscillator

Compact and universal

Published in issue 341, March 2005

Serially Programmable Crystal Oscillator

The right crystal controlled frequency at the right time: With this DIP outline oscillator there’s no need to wait for a special crystal to be made up. You can program its frequency precisely using the RS232 port of your PC. Low phase noise is a feature that makes this PLL oscillator suitable for demanding RF applications also.

This multipurpose clock generator circuit uses the CY27EE16 programmable oscillator of the CyberClock family of devices from Cypress. Regular readers will remember this chip from the November 2004 issue of Elektor Electronics. The entire oscillator circuit comprises of little more than the clock generator chip together with a voltage regulator and fits neatly onto a small PCB. Altogether it makes an extremely versatile clock generator that will no doubt find a use in many applications. The 10 MHz reference crystal shown in the parts list is fitted to the PCB via a socket. A different value may be substituted if it is necessary to provide two or more specific output frequencies simultaneously for a particular application.

Components

Free downloads

Resistors:

R1 = 1kΩ5

R2-R8 = 220Ω

R9 = 10kΩ

R10,R11 = 1kΩ

Capacitors:

C1 = 1µF 16V, radial

C2,C3 = 22pF

C4 = 100nF

Semiconductors:

D1-D34 = LED, 3mm, low current, red

T1 = BC547

IC1 = ULN2803

IC2 = 4023

IC3 = AT90S2313-10PC, programmed, order code 030410-41

Miscellaneous:

S1 = on/off switch, one contact

S2-S8 = pushbutton, PCB mount, 1 contact, 5mm, e.g., T60 (Conrad Electronics # 700479) 

X1 = 4MHz quartz crystal

BZ1 = 5VDC (active) buzzer

BT1 = 2 x penlight (AA) battery with holder

Enclosure, e.g., Hammond type 1591DTRD (150 x 46 x 84mm)

PCB, ref. 030410-1, from The PCBShop