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TIDA-01371: Questions on TIDA-01371

Mir Hossein Ghoreishi
Intellectual 490 points
Part Number: TIDA-01371

Hello,

Checking TIDA-01371 design, I have some questions:

1) There are two VCTRL inputs to set the positive and negative regulators. Why is it two inputs? Why not making a tracking negative regulator, or why not both set by single VCTRL.

2) The feedback loop for positive output sets the "positive virtual ground" and the positive output is this voltage plus positive regulator output which is +3.3V. But the feedback loop for negative output sets the negative output. Why are these loops different.

3) the regulators are set to +3.3V DC, what are the selection criteria for this voltage?

4) The regulators are selected to be very low noise, obviously the output noise is the sum of noises of regulator section and virtual ground section. What is the noise value and stability of virtual ground section?

With Regards,

MHG

 

  • 0
    TI__Genius 12855 points

    Hello MHG,

    Thank you for your interest in TIDA-01371. Please find my answers as below:

    1) You are right. Both the VCNTL signals can be combined and they can be set using a single voltage. We wanted to make two separate circuits on the reference design so that user's can build their own power supplies for +Ve as well as -Ve.

    2) Again, two different circuits were built to show variety. The gain resistors can be selected as per the requirement.

    3) There is no reason for selecting 3.3V. You can select the value using feedback resistors.

    4) For best noise performance, the ground has to be low-impedance path. Since the virtual ground circuit is used, the noise performance will not be as good as having a proper ground. Please note that the application is for getting high-current pulsed load (for 1ms or so) where transient response was important.

    Let us know, if you would like to have TINA files for the circuits used in TIDA-01371.

    BTW, we do have a training video which shows explanation of this circuit. If interested, please look at https://training.ti.com/floating-regulators-support-high-voltages

    Thank you.

    Regards,

    Sanjay R. Pithadia

  • 0 in reply to Sanjay Pithadia
    Intellectual 490 points

    Hello Sanjay,

    Thank you for quick reply and also the video link.

    My question almost covered. But I believe if there is no technical issue, it would be better for design symmetry to use same transfer function for positive and negative outputs. In this design you have:

    Vout(p) = Vctl(p)*20 + 3.3V

    Vout(n) = Vctl(n)*20

    But as you mentioned, no big issue.

    I just downloaded the design files in Altium. And I would like to have the TINA files.

    Thank you.

    Regards,

    MHG

  • 0 in reply to Mir Hossein Ghoreishi
    TI__Genius 12855 points

    Negative-LDO-Virtual-GND.TSC

    Positive-LDO-Virtual-GND.TSC

    Thank you MHG.

    Please find the attached TINA files for the floating circuits.

    Regards,

    Sanjay R. Pithadia