• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 65 subscribers
  • Views 298 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PTH08T250W: [FAQ] Power sequence design

Fu Mandy
Prodigy 40 points
Other Parts Discussed in Thread: PTH08T250W, TL7712A

rt Number: PTH08T250W

Hi, everyone, 

I have design a power sequence circuit, but I am not sure that the design is correct or not, plz help me to check, thanks a lot

Here is my thought :

I use 3 TL7712As to control 3 PTH08T250Ws (3 sets controlling circuits), 

first one TL7712a pin5 connect to PTH08T250W Pin20, TL7712a set delay 1.3ms (the second picture),

second and third objects are designed the same, but Ct (delay setting) are 28.6ms and 61ms (show second picture, but Ct values are different, Power modules' output power different).

Power module output voltages are different, but in range 0.7~3.6V

I think PTH08T250W Pin20 (Track pin) to up are like this below, it is controlled by TL7712A (which is 12V voltage supply, delay time are 1.3ms, 28.6ms, 61ms),

Track pin (PTH08T250W Pin20 be active needs 20ms)

I hope my design is correct, thanks

  • 0
    TI__Expert 8130 points

    Hello Fu,

    I want to begin by making sure I am understanding your application correctly.

    • Are you aiming for a Simultaneous Sequencing or Sequential Sequencing? (The Auto-Track™ function allows for Simultaneous Sequencing)
    • Are all of the Modules adjusted for same output voltage? Please provide more detail on the image plot you provided. What are the voltage values of Red, Orange, Navy? These Modules are only rated for an output voltage of 0.7 V to 3.6 V

    Regards,
    Alejandro

  • 0 in reply to iAlejandro
    Prodigy 40 points

    Hi, Alejandro,

    1. Sequential Sequencing (I have 3 set the same but delay differently timing, 1.3ms, 26.8ms, 61ms by different value Ct, and the first picture shows, is that wrong direction?)

    2.Not the same voltage, all include in 0.7~3.6V range, but 3 different voltages.

    3. The first picture I wanna show you that Power module pin20 Track net begin at different time (1.3ms,26.8ms,61ms). Track Net be active needs 20ms, I use TL7712A to control, it needs 12V voltage supply.

    4. Second picture shows one of my set design, the others are the same design way, just different Values of Ct, Power Module Output Voltages 

    Thank you,

    Mandy

  • 0 in reply to Fu Mandy
    TI__Expert 8130 points

    Understood; it should work as intended.

    Just make sure to have the correct values for Ct to get the desired delay from supply-voltage-supervisor (SVS). The calculations can be made by using the equation on Section 8.3.2 of SVS datasheet.

  • 0 in reply to iAlejandro
    Prodigy 40 points

    Hi, Alejandro,

    Thanks for your replying, but I still have some questions to clarify and want to make sure that my description is right, 

    1. PTH08T250W pin20 Track will be active after it is got the voltage? (Description as below)

           if TRACK pin is connected to VI,it will be taken 20ms to enable when the VI is got the voltage.

     or

          if TRACK pin is connected to external controlling IC/ Switch, it will be taken 20ms to enable when the controlling IC/switch is set ON, no matter VI is power on before the TRACK pin.

    or

         if TRACK pin is connected to external controlling IC/ Switch, it will be taken 20ms to enable when the VI is got the voltage.


    2. PTH08T250W pin19 TT pin leave NC if it is no-used, the Co leave 680uF, otherwise, Change the Co value with Table. 5 (page19)

    3. PTH08T250W pin22 SmartSyn. pin is connected to GND, if I want to these power modules work at different time

    4. PTH08T250W pin21 UVLO/inhibit pin leave NC, if I don't need to change Reference Voltage to shut down the power module, and no inhibit function

    if you can answer these questions, I think the Power sequence circuit will be completed and correct.

    I will check the Ct values of TL7712A , 

    BR, 

    Mandy

  • 0 in reply to Fu Mandy
    TI__Expert 8130 points

    Hi Mandy,

    I want to reinstate what I said earlier about your application: After further review, the condition that will not work as desired is track of Red outline from first image you provided. The module cannot follow a voltage at its track control input until it has completed its soft-start initialization which takes about 20 ms from the time that a valid voltage has been applied to its input. It it is recommended that the Track pin be held at ground potential (at least 20ms) during that time.

    1. According to your schematic: TRACK pin is connected to an external SVS. If it is unused, this input should be connected to Vi (Pin 6,7,14, or 15). Track pin becomes active after a valid input voltage (default: UVLO of 4.3V) has been applied. In your application, the SVS adds a delay from the point that a valid input voltage (4.3 V) has been detected. That is why the first track voltage (red outline) will not work properly due to a minimum of 20ms is required while your delay is set to 1.3ms.
    2. Correct; leave pin 19 open circuit if not used, minimum Cout of 660µF is required, and Table 5 is for turbo trans applications.
    3. Correct; leave pin 22 connected to GND. It is used when synchronizing switching frequency across multiple devices.
    4. Correct; the default UVLO threshold is 4.3 V.

    Regards,
    Alejandro

  • 0 in reply to iAlejandro
    Prodigy 40 points

    Hi,Alejandro,

    It is really helpful, I am really appreciated your replying,

    Thank you,

    BR,

    Mandy

  • 0 in reply to Fu Mandy
    TI__Mastermind 47060 points

    Hi Mandy,

    Thank you for using the E2E forum.  It looks like Alejandro was able to resolve your issue.

    I will be closing this thread now.

    Regards,

    Jimmy