T M S3 2 0 VC5 402
F I X ED ĆPOI N T DI G I TAL S I GN AL PRO CE SSO R
SPRS079E – OCTOBER 1998 – REVISED AUGUST 2000
internal oscillator with external crystal
The internal oscillator is enabled by connecting a crystal across X1 and X2/CLKIN. The frequency of CLKOUT
is a multiple of the oscillator frequency. The multiply ratio is determined by the bit settings in the CLKMD register.
The crystal should be in fundamental-mode operation, and parallel resonant, with an effective series resistance
of 30 Ω and power dissipation of 1 mW.
The connection of the required circuit, consisting of the crystal and two load capacitors, is shown in Figure 10.
The load capacitors, C and C , should be chosen such that the equation below is satisfied. C in the equation
1
2
L
is the load specified for the crystal.
C1C2
(C1 ) C2)
CL +
recommended operating conditions of internal oscillator with external crystal (see Figure 10)
MIN
MAX
UNIT
f
Input clock frequency
10
20
MHz
clock
X1
X2/CLKIN
Crystal
C
C
2
1
Figure 10. Internal Oscillator With External Crystal
36
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