CSP1027 Datasheet, PDF (38/64 Pages) Agere Systems – CSP1027 Voice Band Codec for Cellular Handset and Modem Applications

CSP1027 Voice Band Codec for
Cellular Handset and Modem Applications
Data Sheet
December 1999
7 Application Information (continued)
7.4 Crystal Oscillator
If the option for using the external crystal is chosen, the following electrical characteristics and requirements apply.
7.4.1 External Components
The crystal oscillator is enabled by connecting a crystal across XLO and XHI, along with one external capacitor
from each of these pins to ground (see Figure 30). For most applications, 10 pF external capacitors are recom-
mended; however, larger values may be necessary if precise frequency tolerance is required (see Section 7.4.5 on
page 43). The crystal should be either fundamental or overtone mode, be parallel resonant, have a power dissipa-
tion of at least 1 mW, and be specified at a load capacitance equal to the total capacitance seen by the crystal
(including external capacitors and strays). The series resistance of the crystal should be specified to be less than
half the absolute value of the negative resistance shown in Figures 31 or 32 on page 39 for the crystal frequency.
The frequency of the internal clock will be equal to the crystal frequency.
XLO
XHI
XTAL
C1
C2
Figure 30. Fundamental Crystal Configuration
5-7609 (F)
7.4.2 Power Dissipation
Figures 33 and 34 on page 40 indicate the typical power dissipation of the on-chip crystal oscillator circuit versus
frequency.
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Lucent Technologies Inc.