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TRS202E: Charge pump switching frequency

Daisuke Higa
Genius 4315 points
Part Number: TRS202E
Other Parts Discussed in Thread: MAX3221E,

Tool/software:

Hi support team all.

Could you tell me charge pump switching frequency for TRS202E and MAX3221E?

The reason for asking is to make sure there is no effect on other circuits in the system.

Best regards,

Higa

  • 0
    Guru 316690 points

    The internal frequency of many RS-232 transceivers is nominally 500 kHz (the TRS202E outputs higher voltages and might be different). But the charge pump is regulated, so the actual frequency will be lower. A previous question showed a typical ripple frequency of about 15 kHz, but this might change depending on your actual load current.

  • 0
    TI__Genius 13402 points

    Hi Higa-san,

    Generally the switching frequency can be in the 100-500kHz range. However, we do not specify this value because it varies with the load on the device. From an EMI/EMC perspective, the frequency and energy is low enough that this should not be a concern assuming you follow all datasheet guidelines.

     

    Here are a couple of suggestions to help minimize EMI if you are still concerned:

    - Tie a 0.1uF capacitor to ground on the VCC pin. This helps to filter out noise on the VCC line when the charge pumps are switching. 

    - Ensure the charge pump traces are as short as possible. 

     

    This document details how the charge pumps work and specifically how a control loop is used to change the frequency depending on the load.

    Best,

    Ethan