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SYSTEMCLOCKANDRESETFUNCTIONS
SYSTEMCLOCKINPUT
t
w(sckh)
系统 时钟
t
w(sckl)
2 v
0.8 v
H
L
系统 时钟
脉冲波 循环
Time
(1)
T0005A08
SYSTEMCLOCKOUTPUT
PCM1609A
SLES145–AUGUST2005
thepcm1609arequiresasystemclockforoperatingthedigitalinterpolationfiltersandmultileveldelta-sigma
modulators.thesystemclockisappliedatthesckiinput(pin38).Table1showsexamplesofsystemclock
frequenciesforcommonaudiosamplingrates.
Figure19showsthetimingrequirementsforthesystemclockinput.foroptimalperformance,itisimportantto
useaclocksourcewithlowphasejitterandnoise.thepll170xmulticlockgeneratorfromtexasinstrumentsis
anexcellentchoiceforprovidingthepcm1609asystemclock.
table1.systemclockratesforcommonaudiosamplingfrequencies
samplingfrequencysystemclockfrequency(f
SCLK
)(mhz)
(khz)
128f
S
192f
S
256f
S
384f
S
512f
S
768f
S
8
(1)(1)
2.0483.0724.0966.144
16
(1)(1)
4.0966.1448.19212.288
32
(1)(1)
8.19212.28816.38424.576
44.1
(1)(1)
11.289616.934422.579233.8688
48
(1)(1)
12.28818.43224.57636.864
96
(1)(1)
24.57636.86449.152
(1)
19224.57636.864
(1)(1)(1)(1)
(1)thissystemclockisnotsupportedforthegivensamplingfrequency.
SYMBOLPARAMETERMINMAXUNIT
t
w(sckh)
systemclockpulseduration,high7ns
t
w(sckl)
systemclockpulseduration,low7ns
(1)1/128f
S
,1/256f
S
,1/384f
S
,1/512f
S
,and1/768f
S
.
figure19.systemclocktiming
abufferedversionofthesystemclockinputisavailableatthesckooutput(pin39).sckocanoperateat
eitherfull(f
SCKI
)orhalf(f
SCKI
/2)比率.thesckooutputfrequencycanbeprogrammedusingtheclkdbitof
register9.thesckooutputpincanalsobeenabledordisabledusingtheclkebitofregister9.ifthescko
outputisnotrequired,itisrecommendedtodisableitusingtheclkebit.thedefaultissckoenabled.
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