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TPS62827: TON_MIN, TOFF_MIN

Ben Huang1
Intellectual 705 points
Part Number: TPS62827
Other Parts Discussed in Thread: TPS62130,

Tool/software:

Hi

Some datasheets generally show the information as TON_MIN (minimum on time), and TOFF_MIN (minimum off time).

1. Could you please point out where it is?

2. Other than the specification, we intended to check the specification on our platform, what can we do for the electrical validation? Execute the load transient, short circuit, or anything else? 

3. What is your recommendation in expert opinion?

Any comment is welcome!

Thanks

Regards

Ben

  • 0
    TI__Guru*** 147250 points

    Hi Ben,

    Usually, we don't specify these values for a device that uses the DCS-Control topology.  The minimum on and off times would just affect the switching frequency, as explained here: https://www.ti.com/lit/an/slyt646/slyt646.pdf 

    Is this a concern for your application?

    Thanks,

    Chris

  • 0 in reply to Chris Glaser
    Intellectual 705 points

    Hi Chris

    Thanks for your document!

    It is great helpful to me for a better understanding of the relation among frequency variants, on time, and off time.

    The discussion in the application report focused on TPS62130 which has a wider application range compared to TPS62827, making it flexible for

    identifying the TON_MIN, TOFF_MIN

    After reading the document, may I conclude as follows?

    (1) How to get the TON_MIN?

    While in the low-duty cycle application (Low VOUT and High VIN)

    Increasing VIN and keeping VOUT fixed until the output cannot keep regulation

    (2) How to get the TOFF_MIN?

    While in the high-duty cycle application (VOUT is close to VIN)

    Decreasing VIN and keeping VOUT fixed until frequency turns out to be lower

    Our application now is VIN = 5V, VOUT = 1V, IOUT = 4A

    For our application, is it also possible to check the TOFF_MIN?

    What will you do for this purpose in the given condition (VIN = 5V, VOUT = 1V)?

    Usually, I found the consecutive double pulse behavior of buck converter with on time-based (other manufacturers), that is unstable switching; whether the off time within the double pulse is exactly the minimum off time?

    I am curious about the assumption

    Regards

    Ben

  • +1 in reply to Ben Huang1
    TI__Guru*** 147250 points

    Hi Ben,

    I'm glad you liked the app note.

    The device always regulates Vout.  If an on or off time limit is reached, it will reduce the frequency.  The D/S has graphs showing how the frequency varies--figures 8-23 through 8-28.  Figure 8-28 is closest to your conditions and shows no frequency reduction due to minimum on time.

    Chris