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SN6505A-Q1: Multiple-output push-pull configuration

Jessica Riley66
Prodigy 110 points
Part Number: SN6505A-Q1
Other Parts Discussed in Thread: SN6505A

Hello,

I would like to use the SN6505A-Q1 device to isolate 5V and generate a 5V and 10V output voltage.  Is it possible to use a single transformer solution as shown below?  It seems to work well in simulation, but I am concerned I might be missing something re. balancing the load currents through the transformer.

  • 0
    TI__Genius 17100 points

    Hi Jessica,

    Thank you for posting to E2E! What are the expected current loads on each isolated power rail? Which load conditions have been simulated?

    This topology can yield the expected output voltages, but please share the information requested above and allow me to verify with our team if there are any load-balancing concerns.

    Respectfully,

    Manuel Chavez

  • 0 in reply to Manuel Chavez
    Prodigy 110 points

    Thank you for the quick response.  

    I am considering using this circuit in two places: 

    1. Low current 5V/10V:
      1. 10V: 6V-12V output voltage range w/ 30mA max load, 15mA typical, 0.5mA minimum
      2. 5V: 3.1V-5V output voltage range w/ 15mA max load, 6mA typical, 1.6mA minimum

    2. High current 5V/10V:
      1. 10V: 7V-35V output voltage range w/ 100mA max load, <1mA typical
        1. Includes a high output bulk capacitance ~3.3mF, so soft-start required for limiting current at turn-on
      2. 5V: 4.5V-5.5V output voltage range w/ 500mA max load, 100mA typical, 10mA minimum

  • 0 in reply to Jessica Riley66
    TI__Genius 17100 points

    Hi Jessica,

    Under typical conditions, the circuit is expected to operate normally. Please do ensure to place the 10uF capacitor as closely as possible to the transformer's primary center tap in PCB layout, and feel free to add another 1uF-10uF capacitor on the SN6505A's Vcc pin as a bypass capacitance.

    How are the >10V outputs realized? For the 35V output, SN6505 will not be able to supply a continuous max load of 100mA. If the 100mA is a brief transient, on the order of 10s of milliseconds, then the bulk capacitance should be able to supply this.

    Please let me know your additional concerns.


    Thank you,
    Manuel Chavez