Building a 5V regulator with TLV1117-50

Discussion in 'The Projects Forum' started by swdj25, Jul 17, 2013.

  1. swdj25

    Thread Starter New Member

    May 31, 2012
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    0
    Hello,

    I'm facing some difficulties understanding a circuit for dropping 7.5V to 5V using TLV1117-50. I couldn't find the circuit for TLV1117-50 (the fixed value package) so using the circuit for adjustable package found on page 11 of its datasheet http://www.ti.com/lit/gpn/tlv1117-50 suggests resistors' and capacitors' value. Here is the circuit:

    [​IMG]

    My questions are:

    1. Am I right to take this circuit as the reference even so it's for an adjustable package not the fixed 5V output package? Or there are specific circuits better to follow?

    2. Seeing the VOUT equation suggested below the reference circuit:

    VOUT = VREF(1 + (R2/R1)) + (IADJ * R2)

    how to define R1 and R2 values?

    Thanks for taking a look.
    s.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,000
    3,229
    If you want 5V out from the TLV1117-50, just connect the ADJ pin to ground. You don't need R1 and R2 or Cadj, but be sure to add the input and output decoupling capacitors.
     
  3. swdj25

    Thread Starter New Member

    May 31, 2012
    14
    0
    Thanks crutschow.

    Here I've made a schematic with decoupling capacitors as suggested.
    [​IMG]
    I suppose this can also be applied to the tlv1117-33, right?
     
  4. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    1,758
    98
    That'll work.

    Also add a couple of filter caps as shown in the datasheet.
     
  5. swdj25

    Thread Starter New Member

    May 31, 2012
    14
    0
    Thanks blueroomelectronics.
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    The diode is only needed if the user can accidentally short the Vin pin to ground, ie if you have an unprotected plug/socket on the input. Otherwise you can lose the diode.

    Also I would use larger caps, 47uF on the input and 100uF on the output. You can leave the 0.1uF caps there as well, and just add electros. :)
     
  7. crutschow

    Expert

    Mar 14, 2008
    13,000
    3,229
    Yes, that circuit works for any of the fixed output voltage devices. Only the variable output voltage one needs the resistors to set the voltage.
     
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