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SN65C3232E: C1+ to C1- Voltage

Tyler Holmvik
Intellectual 811 points
Part Number: SN65C3232E

Tool/software:

Hello,

Can you help me understand the C1 capacitor function?

What is the expected voltage measurement between pins C1+ and C1- ? What does that depend on? Is it a constant voltage?

Thanks,

Tyler

  • +1
    TI__Mastermind 48327 points

    Hi Tyler,

    That capacitor is the flying capacitor of the charge pump - please see this tech note for more detailed information: https://www.ti.com/jp/lit/pdf/SSZT674 

    Charge pumps generally have a flying a storage capacitor. 

    We spec almost nothing about the charge pumps on any of our RS-232 devices - designers need to follow datasheet recs. exactly on those pins - if there is an issue on the C#+/C#- pins it will show up on V+/V- rails where are just DC voltages and should be close to VOUT for bus pins (a little larger in magnitude).  Essentially don't measure these pins because we have no spec's for them really and any issue there will propagate onto pins that we have more concrete advice for (like V+/V- or bus output voltages)

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Intellectual 811 points

    Thanks for the context. Also that app note is great. 

    Tyler