Datasheet

X1 X2
R1
CL2CL1
DP83640
www.ti.com SNOSAY8E –SEPTEMBER 2007–REVISED APRIL 2013
A 25 MHz, parallel, 20 pF load crystal resonator should be used if a crystal source is desired. Figure 9-3
shows a typical connection for a crystal resonator circuit. The load capacitor values will vary with the
crystal vendors; check with the vendor for the recommended loads.
The oscillator circuit is designed to drive a parallel resonance AT cut crystal with a minimum drive level of
100 µW and a maximum of 500 µW. If a crystal is specified for a lower drive level, a current limiting
resistor should be placed in series between X2 and the crystal.
As a starting point for evaluating an oscillator circuit, if the requirements for the crystal are not known, C
L1
and C
L2
should be set at 33 pF, and R
1
should be set at 0 Ω.
Specification for 25 MHz crystal are listed in Table 9-3.
Figure 9-3. Crystal Oscillator Circuit
Copyright © 2007–2013, Texas Instruments Incorporated Design Guidelines 73
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