• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 62 subscribers
  • Views 471 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TPS54332 behavior when Vin == Vout.

Jeroen3
Prodigy 60 points
Other Parts Discussed in Thread: LM2596, TPS54340

I'm exploring ways to design a 12V LED strip driver (with USB control). My goal is to be able to dim the LED's as if it was a constant current source.
Current thoughts are that the way to do this is by injecting current into the feedback divider, offsetting the feedback voltage positively, reducing the output voltage. (assuming the attached load is unkown)
However, when no dimming is selected the Vin == Vout. Since the source is a 12V wall plug or ATX supply.

While running a quick test on a LM2596 there was a 1 Volt drop in output voltage, with heat dissipation.
Is this behavior to be expected with the TPS54332 (or similar)? 

And is the device relying on the Vout ripple to charge the boot capacitor?

  • 0
    TI__Guru**** 191445 points

    Max duty cycke is 90-93% so at 12 V input maximum output is about 10.8 V.  You may want to look at TPS54340.  It can support 100% duty cycle as long as the BOOT charge holds.  BOOT is refreshed by the switching node going low, not by any Vout ripple.

  • 0 in reply to JohnTucker
    Prodigy 60 points

    The TPS54340 seems ok, bit more expensive though.

    So the maximum duty cycle is a little below 100% when using normal boot pin capacitor.
    And will be 100% when applying Vin + 2.1 V from external source.

    Thanks, I'll see if it works.