• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 223 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.

TPS560200-Q1: time accuracy of 2-ms Internal Soft Start

Christian Sch.
Prodigy 60 points
Part Number: TPS560200-Q1
Other Parts Discussed in Thread: TPS560200

Hello,

I'm using the TPS560200 as an external core supply of 1.2 V for the Infineon TLF35584. The TLF35584 enables the TPS560200 and observes its output voltage. It has a short to ground detection with 3 ms (2.7 to 3.3 ms tolerance), that expects a sufficient voltage after enabeling the external step down converter.

We built already several control boards with this setup, but now there is one board that does not start properly because of a too slow TPS560200.

The picture below shows a working combination: After reaching 3.3 V at the line UB3V3 the TPS560200 is enabled and it ramps up the line UB1V2 to 1.2 V within 2.76 ms. The time between 0.2 V and 1.0 V (1/6 to 5/6 of output voltage) is 1.485 ms, so the full soft start time between 0 V and the final voltage of 1.2 V would be 2.228 ms.

The picture below shows the failing combination: After reaching 3.3 V at the line UB3V3 the TPS560200 is enabled and it ramps up the line UB1V2 to 1.2 V within 3.63 ms. The time between 0.2 V and 1.0 V (1/6 to 5/6 of output voltage) is 2.147 ms, so the full soft start time between 0 V and the final voltage of 1.2 V would be 3.22 ms.

The circuits and all sourrounding conditions are identical, nothing is changed.

The data sheet tells:

Internal Soft-Start (VSENSE ramps from 0 V to 0.8 V): 2 ms (typical)

Unfortunately there are no Min. and Max. values mentioned. What could be the maximum ramp up time?

Is this a faulty TPS560200, or would this device still be considered OK?

  • 0
    TI__Genius 12951 points

    Hi 

    The max SS time is about 3.5ms. It is a normal device. 

    Shuai

  • 0 in reply to Shuai Fan
    Prodigy 60 points

    Hi,

    I just added a measurement to Vsense.

    Here is one try to start the supply which is abortet by the TLF after 3 ms. You can see that Vsens doesn't reach 0.8 V after at least 2.7 ms. (Unfortunaltely I can't measure the enable signal, but it must get high somewhere between UB3V3 is correct and UB1V2 is rising.)

    The second try to start the supply was successful by the TLF. But you can see, that the soft start ramp up takes more than 3 ms.

    Here is photograph of the device. It is markes with "TI 79 ZDNK".

    But you say that a SS time of up to 3.5 ms is OK? Than unfortunately I have to change the step down converter to a faster type.

    Christian

  • 0 in reply to Christian Sch.
    TI__Genius 12951 points

    Hi Cristian!

    Actually, I didn't understand what is your question by above description.

    Shuai

  • 0 in reply to Shuai Fan
    Prodigy 60 points

    Hi Shuai,

    I just added this post because first I was asked by someone to also measure Vsense and to send a picture of the device. It was expected, that the soft start time range should be within +/- 10 %. But this answer doesn't exist any more in this topic.

    But yes, you said that up to 3.5 ms have to be considered as OK. So it is clear to me that I have have to change to a faster device.

    Christian

  • 0 in reply to Christian Sch.
    TI__Expert 8100 points

    Hi Christian,

    My colleague will give you reply by next week!

    BRs

    Zixu