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SYSTEMCLOCKANDRESETFUNCTIONS
SystemClockInput
t
(sckh)
系统 时钟
t
(sckl)
2 v
0.8 v
H
L
系统 时钟
脉冲波 循环
Time
(1)
t0005-08
pcm1780,pcm1781,pcm1782
SLES132A–MARCH2005–REVISEDAPRIL2005
thepcm1780/81/82requiresasystemclockforoperatingthedigitalinterpolationfiltersandmultilevel
delta-sigmamodulators.thesystemclockisappliedatthesckinput(pin5).table1showsexamplesofsystem
clockfrequenciesforcommonaudiosamplingrates.
figure20showsthetimingrequirementsforthesystemclockinput.foroptimalperformance,itisimportantto
useaclocksourcewithlowphasejitterandnoise.德州仪器’spll170xfamilyofmulticlockgeneratorsisanexcellent
choiceforprovidingthepcm1780/81/82systemclock.
table1.systemclockfrequenciesforcommonaudiosamplingfrequencies
samplingsystemclockfrequency(f
SCK
),mhz
频率
128f
S
192f
S
256f
S
384f
S
512f
S
768f
S
1152f
S
8khz1.0241.5362.0483.0724.0966.1449.216
16khz2.0483.0724.0966.1448.19212.28818.432
32khz4.0966.1448.19212.28816.38424.57636.864
44.1khz5.64488.467211.289616.934422.579233.8688–
(1)
48khz6.1449.21612.28818.43224.57636.864–
(1)
88.2khz11.289616.934422.579233.8688–
(1)
–
(1)
–
(1)
96khz12.28818.43224.57636.864–
(1)
–
(1)
–
(1)
192khz24.57636.864–
(1)
–
(1)
–
(1)
–
(1)
–
(1)
(1)thissystemclockfrequencyisnotsupportedforthegivensamplingfrequency.
(1)1/128f
S
,1/256f
S
,1/384f
S
,1/512f
S
,1/768f
S
,or1/1152f
S
PARAMETERMINTYPMAXUNIT
t
(sckh)
systemclockpulseduration,high7ns
t
(sckl)
systemclockpulseduration,low7ns
figure20.systemclockinputtiming
12