Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

  • State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 66 subscribers
  • Views 281 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.

LMR23615: Dropout

Jacob Olstad
Intellectual 1270 points
Part Number: LMR23615

Hi,

Trying to track down what kind of dropout to expect from the LMR23615 in the below conditions:

Vin = Vout = 12V, Iout = 1.5A

The datasheet talks about frequency foldback and gives a curve for a 5V out condition.  Would we expect a similar voltage drop for any Vout?

Thanks,

Jake

  • 0
    TI__Prodigy 480 points
    Hi Jake,

    It would be different, and I can test the part at Vout=12V, Iout=1.5A. However, the Vin cannot go as low as 12V in your case because it would exceed the duty cycle.
  • 0
    TI__Mastermind 25590 points

    Jacob,

    For VOUT = 5V, IOUT = 1.5A WEBENCH lets me make a design with 5.8VIN but not 5.7VIN which is conservative compared to the datasheet (~5.4V).

    For VOUT = 12V, IOUT = 1.5A WEBENCH lets me make a design with 13.5VIN but not 13.4VIN so we might expect between ~12.4V and ~12.7V.

    I exported the 13.5VIN WEBENCH design to TINA and sim'd a dropout condition and saw a droop in VOUT at VIN = 12.45V so that's probably the best estimate. This could be tested on the EVM but this sim might line up better with the EVM than the EVM with the customer board.

    -Sam

  • 0 in reply to Samuel Jaffe
    TI__Intellectual 1270 points
    Hi Sam/Eric,

    I understand that Vin = Vout = 12V is not realistic. What i'm trying to understand is how much dropout voltage i should expect when Vin = 12V.

    From some quick math I'm think around 600-700mV sounds about right.
    max duty cycle = 97% and ron (top fet) = 160mohm
    12*.97+1.5*.160 = 640mV

    Is my math accurate? ie with a 12V input and a 12V set point at 1.5A I would expect a final output voltage of around 11.3V.

    Thanks,
    Jake
  • 0 in reply to Jacob Olstad
    TI__Mastermind 25590 points
    Jacob,

    My sim shows 12.45Vin gets you 12VOUT barely. So I'd expect a similar dropout for VIN=12V --> VOUT = 11.55V but this might not take everything real into account. Your value of 11.3V is a good estimate.

    -Sam