CSR8635 查看數據表（PDF） - CSR plc

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CSR8635

The CSR8635 QFN single-chip Bluetooth® audio ROM device targets mid-range stereo speakers and headsets.

CSR plc 

Note:

Excessive amplifier transconductance can lead to an increase in the oscillator phase noise if the oscillator amplifier

is excessively overdriven. Set the transconductance to the minimum level to give the desired oscillation ratio. Higher

values can increase power consumption. Also, insufficient drive strength can prevent the the crystal from starting

to oscillate.

3.1.1 Negative Resistance Model

The crystal and its load capacitor can be modelled as a frequency dependant resistive element. Consider the driver

amplifier as a circuit that provides negative resistance. For oscillation, the value of the negative resistance should be

greater than that of the crystal circuit equivalence resistance. Equation 3.1 shows how to calculate the equivalent

negative resistance.

3TWPTCaPFIw.hnra1ibrnaaheierltt.rnei■■■■■airqc2aaesmhu3lm:cFe.eoc3enrtgCCCCanteecsemndoiioCrqnnyhruutu=b=ot=rc=ee=wytSTInaOnsscIrtcnnaPatonteytcttnhamr-eirececesenrlphcprnacrsSeoiaaaloppnnlrcprpesepdcaafceaadraupcoitrTpfccaieiafmtctaaoacdiasafcbirnintinfttiaclcoqtiiecoocanearMiemnnn3cc2-oticgoe.ainfi2nfeoofbpo:atrtRoahnohnTlacennfekrnrXieateecXcagTneqrvrn=TEysAxyuec−sAcqtsLeneetoutL2a_n.arnaz_bInπlcl,NdhtOeayofiwuo,2otlUswc(nhsuccCTteeiriac3yl-,oeelhn.Tas1use1ncTtty-t.ei:xaoCs5epaiencNlr.ibsanepaeTgol+Mneulm1gapmm(d-t6iaCb3onpCaeOtl.il0ien1nitvifin+nmidte3eC.C-cc.reoR1oiohnsuuemittpt)rsp(e.iCuPcsfettnoaarourrn-afte+cTsFXd2Ceiy-rTt6MiitpicdnoA--a)aCL)axy2saa,pmtShapeeclpiitsfatiheenurmc.n±eMbt32eoa28rrx52ca7s, e20ca1pU3mpanFScitiMptUapHnnmiczt e

Frequency Stability

-

-

±20

ppm

Crystal ESR

-

-

60

Ω

Table 3.3: Crystal Specification

3.1.3 Crystal Calibration

The actual crystal frequency depends on the capacitance of XTAL_IN and XTAL_OUT on the PCB and the CSR8635

QFN, as well as the capacitance of the crystal.

The Bluetooth specification requires ±20ppm clock accuracy. The actual frequency at which a crystal oscillates contains

two error terms, which are typically mentioned in the crystal device datasheets:

Production Information

© Cambridge Silicon Radio Limited 2013

Confidential Information - This Material is Subject to CSR's Non-disclosure Agreement

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