APR6SLASHD datasheet(23/101 Pages) NXP

23 / 101 page

DSP56001A

External Clock (EXTAL Pin)

MOTOROLA

DSP56001A/D, Rev. 1

2-5

EXTERNAL CLOCK (EXTAL PIN)

The DSP56001A system clock may be derived from the on-chip crystal oscillator as shown in

Figure 2-2

, or it may be externally supplied. An externally supplied square wave voltage source

should be connected to EXTAL, leaving XTAL physically unconnected to the board or socket.

The rise and fall times of this external clock should be 4 ns maximum.

Figure 2-2 Crystal Oscillator Circuits

Suggested Component

Values

R = 680 k

Ω ± 10%

C = 20 pf

± 20%

Fundamental Frequency

Crystal Oscillator

3rd Overtone

Crystal Oscillator

Suggested Component Values

R1 = 470 k

Ω ± 10%

R2 = 330

Ω ± 10%

C1 = 0.1

µf ± 20%

C2 = 26 pf

± 20%

C3 = 20 pf

± 10%

L1 = 2.37

µH ± 10%

XTAL = 33 MHz, AT cut, 20 pf load,

Ω max series resistance

Note:

The suggested crystal source is

ICM, # 433163 – 4.00

(4 MHz fundamental, 20 pf load) or

# 436163 – 30.00

(30 MHz fundamental, 20 pf load)

To reduce system cost, a ceramic

resonator may be used instead of

the crystal. Suggested source:

Murata-Erie #CST4.00MGW040

(4 MHz with built-in load capacitors)

Note:

3rd overtone crystal

The suggested crystal source is

ICM, # 471163 – 33.00 (33 MHz

3rd overtone, 20 pf load)

R2 limits crystal current

Reference Benjamin Parzen,

The Design of Crystal and

Other Harmonic Oscillators,

John Wiley & Sons, 1983

XTAL EXTAL

XTAL1

XTAL11

EXTAL

XTAL

AA0886

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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