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SN74CBTLV3257: Signal collision at switching

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Part Number: SN74CBTLV3257

Hi Team,

My customer is evaluating the SN74CBTLV3257 on their board, and they measured signal collision waveform at switching. Could you review their measurement waveform below and let me have your answers?

SN74CBTLV3257 Waveform at signal collision 20200603.xlsx
 
Q1) When switching the S pin, is it possible that both the SW of the B1 pin and the SW of the B2 pin are both turned ON at the same time?

Q2) When switching the S pin, is there something like dead time provided for the B1 and B2 pins so that both do not turn on?

Q3) Regarding this phenomenon, is it possible to prevent signal collision by controlling the /OE pin as shown below?
        '/OE=Low  -->  Switch /OE pin to High  --> Wait 1ms  -->  Switch S pin -->  Wait 1ms  -->  Switch /OE to Low

Q4) Is there a measure other than the method described in Q3)?

Thank you.

Best Regards,

Koshi Ninomiya

  • This device does not do break-before-make switching. All FETs are switched at the same time, so it is possible for them to be partially open during switching.

    It is indeed possible to use OE to introduce a dead time. Please note that tdis + ten is much shorter than 1 ms.

    Consider using another device with the break-before-make feature, e.g., TS3A44159 or TMUX1134.

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