73M1903C Просмотр технического описания (PDF) - Teridian Semiconductor Corporation

Номер в каталоге

Компоненты Описание

Список матч

73M1903C

Modem Analog Front End

Teridian Semiconductor Corporation 

73M1903C

Modem Analog Front End

DATA SHEET

CLOCK GENERATION

Crystal Oscillator and Prescaler NCO

The crystal oscillator operates over wide choice of crystals (from 4.9MHz to 27MHz) and it is first input to

a Numerically Controlled Oscillator (NCO) -based prescaler (divider) prior to being passed onto an on-

chip PLL. The intent of the prescaler is to convert the crystal oscillator frequency, Fxtal, to a convenient

frequency to be used as a reference frequency, Fref, for the PLL. The NCO prescaler requires a set of

three numbers to be entered through the serial port (Pseq[7:0], Prst[2:0] and Pdvsr[2:0]. The PLL also

requires 3 numbers as for programming; Ndvsr[6:0], Nseq[7:0], and Nrst[2:0]. The following is a brief

description of the registers that control the NCOs, PLLs, and sample rates for the TERIDIAN 73M1903C

IC. The tables show some examples of the register settings for different clock and sample rates. A more

detailed discussion on how these values are derived can be found in Appendix B.

LockDet

FXtal

Fref

NCO

prescaler

Up

PFD Kd

Dn

Ichp Control

Charge R1

Pump C1

C2 VCO

Kvco

3

3

Kvco Control

NCO

0

Divide 1

by 2/1

System

Clock

FrcVco

Figure 6: Clock Generation

Page: 17 of 46

© 2005-2008 TERIDIAN Semiconductor Corporation

Rev 4.3

Share Link: