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SN65C3222E: Charge pump circuit

Genius 3110 points

Part Number: SN65C3222E

Dear Technical Support Team,

Could you show the charge pump circuit of SN65C3222E?

ADI' IC shows it.

ADM561_charge_pump.pdf

Best Regards.

ttd

  • Hello ttd,

    The design in SN65C3222E is the same as what is shown in the PDF you attached. To summarize, C1 is used to double the VCC voltage and store it on the V+ node (with C3 used for ripple reduction). C2 is then used to invert the V+ voltage and store it on the V- node (with C4 used for ripple reduction).

    Regards,
    Max
  • Genius 3110 points

    In reply to Max Robertson:

    Hi Max,

     

    Thank you for your reply.

     

    I understand your answer.

    By the way, our customer had a mistake of connection.

    V+ should be connect to GND through capacitor, but V+ connects to Vcc.

    It seems correct operation as RS232 on their system.

    Is it possible to use it? They'd like to know the reason why it affects behavior.

    But I'd like to ask them change of correct connection definitely.

     

    Best Regard,

    ttd

  • In reply to ttd:

    Charge Pump.pdfttd,

    It is OK to connect the V+ capacitor (C3) to VCC instead of ground.  This capacitor is used for filtering, and both VCC and ground can typically serve as stable voltage references.

    By the way, I have attached a drawing of the charge pump circuit for your reference in case it is useful.

    Best regards,

    Max

  • Genius 3110 points

    In reply to Max Robertson:

    Hi Max,

    Thank you for your reply and schematic of charge pump.
    ADI and Maxim connect V+ capacitor (C3) to VCC on datasheet generally.
    Why is TI connect V+ capacitor (C3) to GND on datasheet?
    If you have the reason, could you share it?

    Best Regards,
    ttd
  • In reply to ttd:

    ttd,

    I don't know of a strong reason to recommend either connection method over the other; both connections will work.

    Max