dsp56001a Freescale Semiconductor, Inc, dsp56001a Datasheet - Page 23

• Manufacturer Part Number: dsp56001a
• Description: 24-bit Digital Signal Processor
• Manufacturer: Freescale Semiconductor, Inc

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.
MOTOROLA
Note:
1. The suggested crystal source is
2. To reduce system cost, a ceramic
Suggested Component
Values
R = 680 k
C = 20 pf
Fundamental Frequency
ICM, # 433163 – 4.00
(4 MHz fundamental, 20 pf load) or
# 436163 – 30.00
(30 MHz fundamental, 20 pf load)
resonator may be used instead of
the crystal. Suggested source:
Murata-Erie #CST4.00MGW040
(4 MHz with built-in load capacitors)
Crystal Oscillator
C
XTAL EXTAL
20%
XTAL1
Freescale Semiconductor, Inc.
10%
R
For More Information On This Product,
C
Figure 2-2 Crystal Oscillator Circuits
Go to: www.freescale.com
DSP56001A/D, Rev. 1
Note:
1. 3
2. The suggested crystal source is
3. R2 limits crystal current
4. Reference Benjamin Parzen,
Suggested Component Values
R1 = 470 k
R2 = 330
C1 = 0.1 f
C2 = 26 pf
C3 = 20 pf
L1 = 2.37 H
XTAL = 33 MHz, AT cut, 20 pf load,
50
L1
EXTAL
ICM, # 471163 – 33.00 (33 MHz
3
The Design of Crystal and
Other Harmonic Oscillators,
John Wiley & Sons, 1983
rd
rd
max series resistance
overtone crystal
overtone, 20 pf load)
C3
C2
Crystal Oscillator
3rd Overtone
20%
10%
External Clock (EXTAL Pin)
XTAL1
20%
10%
10%
10%
R1
1
C3
R2
XTAL
DSP56001A
AA0886
2-5