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TRS3232E: Output signal issue at case of Vcc=5V

masahiko shimizu
Guru 11235 points
Part Number: TRS3232E

Hi,

Output signal has issue at Vcc=5V.
Please see below waveform.
Blue is input signal, Purple is output signal.
Do you know the reason why output waveform has ripple?

Best regards,
Shimizu

  • 0
    TI__Guru 62910 points
    Hello Shimizu-san,

    The driver works by pulling the output voltage to the V+ rail to send a high/positive level and by pulling it to the V- rail to send a low/negative level. There is expected to be some ripple on the V+ and V- rails since they are generated based on VCC using a switching charge pump circuit. The level and frequency of ripple will be a function of the charge pump design as well as the external capacitance values and the loading on the RS-232 output. You can read more about the charge pump in this blog:

    e2e.ti.com/.../how-the-rs-232-transceiver-s-regulated-charge-pump-circuitry-works

    Considering this, the waveforms you provided look normal. This should not present issues for communication since even with the ripple the signals will always exceed the high-level and low-level thresholds defined by the RS-232 standard.

    Please let me know if this is not clear or if you have any further questions.

    Regards,
    Max