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作者: iekon 时间: 2005-7-19 14:40 标题: ×?·??????????·?è?????????ê????·???

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1???°??
?????ü???ê??????×????????·?¤????????·???·????????????¤×÷???????????????????±?????±???ì??·???????×??è???ì?ò???????????·????????????×??????ü????×??ó??????????????????????·??ò·??????????ù??????????????????????×??è???????????????????·??????????????±??ó?????????·???????????????á?????????±???????¤×÷?????????????á???????????????????í?????????????????????è????·??????????ü?ò??????×???×??????????????????±?????????????á????????±???????±????????????·°?????????????°????????????????????????°?ì????·????????????????è??????????????°??????°?ì?????????????±????????50MHz?±??????????±????????????????????????¨?????????±???????????????·°?°??????????????ò???????????????è??±??????????????????????±?ò???????°?????????????§?????????ê?????¨?????????????????????ê??????????????????×?PCB?è??±??????????????????????÷????PCB°????????????÷????PCB°????????????????????????????ò???????á?????????ê???????????????????????¤×÷?????¨???????ê?????¤×÷???ò???????????????è?????°°????è???????????????ê???????ò?????????????§?????????????????????±???????è???¤??????PCB?è????????????????????????

2. ?????ê????????????
?????????ê?????¨Signal Integrity,?ò??SI?????????????????????????????????????ê???????????????????ò??????????????°????è?????à???ò???????????????±???·?????????????ó???±?ò???????±????????·ù??????IC?±???????·???????????????ê???????±?????????????ì???±???????????????ê?????????????ó??·???×è?á?????????????·?????????ê?????????á?ì???±???????????????????í?????????·??±??????í??????IC???ó???????±??±????°?ó???????¨×????????????¨×??????????±???????¨???±????±????±????????????×?±????????¨×????ò?ó????±???×?????IC???????ó???ò???§??·???????

??????????±???±í????IC????????????±???????????????±?????IC??????·??ú×???±?????IC???????ò?±??×÷?????????????·°??????????ò?????????????????ò?±??????±????????ó???±?????????¨???????±?????????????????ò???????±???????ú×??????????±??SI???????á???????????????????????????±?????????????????ò???????????ú?ú?????±???±???????????????¨???????±??IC×??????á??±???

????????????????×è?????????á????????·???????????????·?????·???????????????????×è????????×è????·?????????????·?????????????×è???ó????×è????·?????????????????????????×????????·???????????????????÷???????°???????????????????ò????±????ù?á???????à·????????????????¨ringing?????·???????¨rounding???????????????????????????????????????·×è?á×??????·????????????×è?á×?????????1?ù?????????????????·?????????á?ì???ó??·??????????ó???????????????????·???è?????????????????????????????á?ì???????°?ì????????CPLD/FPGA?????ó???????????·?????????á?ì?????????ó??·????°???·?¨?±×?????

??????×????????óIC??°????¨?±?ò???????¨?±?????????????????????????????????????á???????÷???????????????÷?????????????ú?ú?±?????????±???á?°?ìIC???¨???±????±????±??????????·¨???·??????????????2?ù?????????????±?ò?¤??IC???????????????·?????±?????á????IC???í?ó???±?????????????????????±???á?????????????ò?í?ó????????????

?????????????ê???????????á?°?ì????±??í?????????ê??????????????????????PCB°??????????????÷???ò??????????????????(mutual capacitance)?????????±?????÷???ò???ù????????????·??ú±????±????±????á?¨?????????????°?ì?????÷???ò???????????????????????????????÷???°?????????????????à???à?????±?????ò????????×????ó?±???????????????????·???á?????????ê???????????????°?ì???????????????ü???·?????±?????á?????°?ì???????à?????·??????????

???????????????????÷????????PCB°????????à??×??????????????????±(??????×????????·×??????????÷??)????????????????????????×è?????°?÷???????????????á?ú?ú???????????ù??Xilinx ??????SSO(Simultaneously switching outputs)?????°???????????á??????????·??????ù(?ò??????)??SSO?????????????ê???????????????·??I/O??????PCB°???????????????????×è?????°?????÷????PCB°???????????????·?????

????×??????????ê?????????÷??±í????5??·???????????·??????????????????????ù(SSO)????????????(EMI)???????ê????(SI)?????????????????è?????§????????????????±????????·°??è???ê?????ó???????????÷????

3??IBIS????
??????????PCB°?×?°????°·????é?¤°????????ê?????¨SI???????????è???????????ü???????è??????SI·?????°ü???÷????????×??·???????ó?à??SI·????¤????????PCB°?×÷??°?????????????????×???????????·?????????????????????????·???°??????????????÷?????????÷???????????????à????????IBIS????????°??ú?è??????????SI???????è????????×??·????????????·???????????

????IBIS?¨Input/Output Buffer Information Specification?????????????ù??V/I?ú??????I/O BUFFER?ì??×??·?¨????·?·¨????·?????????????????????????????????????????????????????×è????????/?????±???°????????????????·???????×??????????????????§??????????·??????¨??IBIS?????????÷???????ì???á??????IBIS±??í???????????????????ü???÷??????±ê×???IBIS?????????????????????????????÷???????÷?????????????????????÷????±??????????????????????????????è????????IBIS??????·????¤??????????IBIS?á???????ê????V-I?ú??·?±??ú±í?????÷????????????????×????????°???·?¨??×?????????×???×??????ú??????????????IBIS?????????????????¨????

?¨1????I/O·?????·????????á??×??·???????????±??????·?×°?????ú??????ESD?á????
?¨2???á??±??á??????·?·¨?ü?ì??·?????????
?¨3????????????°????ò?à°??????ê????·???·?????????IBIS????·??????????ê????????°ü?¨????????·?????????????????????????????×è??????????·??????????á??·?????IBIS????????????????????????????×??·??????·??????ü???????ì??×????é?????????±???????????????????°???????í??????·¨???????é????
?¨4????????????·???°??????§?????????????§???è???????????????ú?????????????????ò??????±????????????ò???????????¨???÷?????á????????±à??????????
?¨5???????¤??????·???·??????¨??

?????±????IBIS?????ê???????ü???????????±????
?¨1??IBIS?±·??????????ù???¨????????
?¨2???±?????ò°????¤×÷?????ü?ò?ó??800MHz?±??IBIS???????????á?????·????????

4. ??????????????????
??????????????×è?????????á????????·?????????????3?ù?????í??????????????·?????????·???????????????????

????????3???í????????±???×è??RS????×???????????????????????×è????Z0??????×è????RL???í?????é?????±RS=Z0=RL?±??????????×è???????????????á·??ú????·???????????°???????????×èRS?????í??°?????????????×èRL???¨?????????±?÷????????????????×è???ó??????????????×è???????????????à?à?????????á·??????????????????????????ü?????????????????????é?????·×è?á??????????×è??????????????????×è????????????±??±?°?????á?????????ü?à???????????¨??·??????¨???????????ü?à?????????????é????????×è?á???·×è?á????×è?á???á????·??ò???????¨?????????é???????????????á????×¤?¨???±Z0=RL?±???????ê???ü??????????????????????????·????????????????é??????????×è?á?????????è??????????????????????×è?á?é???????ú×????ù??×???????????·??????á??????×è?á???ò???????é??????????·???????????

????·?????????????·ù????????·?????????s??????·?????????L ???¨
??????L = (RL - Z0) / (RL + Z0) ?? ??S = (RS - Z0) / (RS + Z0)

????????????????RL=Z0?ò????·?????????L=0???? RS=Z0????·?????????S=0??

???????????¨????????×è??Z0?¨???? 50??×ó??????????×è???¨???????§?·?·???????§?·?·???ò????????????????×è??????±????§???????????????????????¨??????×è???¨??±????????ó?????????·?·???ò????????????×è???????????×???à??

5. Xilinx?????ê????????·?°?
????Xilinx FPGA?÷????SelectIO?§???à????????????????±ê×???????????±ê×??????á???à?????????÷???±???????????????÷?????±??????????????×è????????4?ù?????±????TTL/CMOS±ê×? 24mA???????÷?±????????×è???ó????13????????????×è??Z0=50??????????????????33??????????????×è??13??+33??=46?? (?ü????50?????????·×è?á???ú????????setup?±??)

?????±????????????±ê×??????????÷?±??????×è???á?????ì???????????????????·?è???±???????????ü???????????±?????????????????????¨?é???¨??????????????×è,????4?ù????

???????????????à?????è?????è·?±????????????í??????5?ù????

???????????????è???????????à????????????×è??????6?ù???????è????????????·????????????é?????±???á?ó?ó?????????¨??°???????±???Xilinx???????ú Virtex-II FPGA??????????????×è???????????¨XCITE-xilinx????????????????????????????×è?÷????????????°???I/O????????????????????×è????????????7?ù???? ??????PCB??????×è??, ?ó?ó????????????±???

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6. ?á??
????×??????????????????ê???????????????????????????ò????????????°??è???±???????è????±??????????¤??????????????×÷??????SI???????????¤?????????????ü?????????????????é??????????????SI????????·?·¨?????????é????IC???????????¨SI?????????????????????????±???ò±?????????????IC×???×???????????IC±??????????ì??????SI?????????????????????·???????÷????????????

????????????SI?è?????¤????????????·????¤?????????????????????????????????°???????????????????????·??·??????????????ú???????±????·????è??·????????·??SI?è?????????????·°????ü??·????è????????????????·????¤???????ü???×????±?SI??????????SI???????ó???????????????·?????????????????????ú??????????SI??????????SI???????è?????????????????????????????ó???±???????????è????±????è??·????????????á?ó?ó???????????????ú?·??±??????ì?ú?·????????·???????SI?????á?ì???????????¨?ò·??ú??????????????????????·??ú?????é??????????·??ú?????§???ò???ú?·????

作者: iekon 时间: 2005-7-19 14:40

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作者: zing 时间: 2005-7-19 18:44

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