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UCC256303: About device ON / OFF

Masazumi Ishii
Genius 3945 points
Part Number: UCC256303
Other Parts Discussed in Thread: UCC256403, UCC256302

Hello

We are considering UCC256303.
I have a question about how to switch on / off the UCC256303.

I want to turn on / off UCC256303.
At this time, I want to start from the soft start at the start.

Question
Is there an application note or reference circuit for this method?

We are investigating whether VCC voltage can be realized by turning it on and off.
・ In this case, what is the voltage at which VCC turns off?
・ When Vcc falls below a certain OFF voltage, it stops and starts at 10.5Vtyp or more.
Do you enter FAULT mode when stopped?

There are other methods, but I don't think it matches the specification.

1 FB → L: When moving from FBpin L → H, isn't soft start activated?
2 BLKpin: H → L Does not start immediately during FAULT mode.

Is this idea correct?

thank you.

  • 0
    TI__Expert 8210 points

    Masazumi-san

    First off we recommend that you use our latest LLC controller UCC256403 instead.  This device is pin to pin compatible with UCC256303 but has many improvements.  Details are in this app note http://www.ti.com/lit/an/slua966/slua966.pdf

    Section 8.3.9 (page 24-27) of the UCC256403 datasheet explains all the fault protections that can cause the IC to shut down.  Exceeding these conditions will cause the converter to shut down if it enters the fault state.

    The easiest way to enable a external signal to disable UCC256403 is to pull BLK pin to ground and trip the Input Under Voltage Protection (VINUVP).  You can implement this with a logic FET connected between BLK and GND, so when the FET is off UCC256403 is enabled and when the FET turns on UCC256403 is disabled.

    Best Regards,

    Eric

  • 0 in reply to Eric Faraci
    Genius 3945 points

    Hello.

    Eric-san

    thank you for your answer.

    I have the following questions regarding the new device UCC256403.

    ・ When is UCC256403 RTM?
    ・ Can samples be provided now?

    Already using UCC256302.
    We are considering the specifications of UCC256303 in a different project this time,
    and are conducting power supply specifications and evaluation.
    Due to the short development period, the new UCC256403 may not be in time.
    Therefore, please give the ON / OFF answer you asked in UCC256303.

    Thank you.

  • 0 in reply to Masazumi Ishii
    TI__Expert 8210 points

    Masazumi-san

    It is against TI policy to publicly disclose production release dates for devices in development such as UCC256403.  For more information on availability and timeline please send me an email at wefaraci@ti.com

    Setting BLK pin to GND to externally disable operation works for both UCC25630x and UCC25640x.  I'm sorry that I did not make that clear in my earlier message.

    Best Regards,

    Eric