• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 64 subscribers
  • Views 1417 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.

About source circuit resister of TPS65145

Satoshi
Guru 19645 points
Other Parts Discussed in Thread: TPS65145

Please let me know about TPS65145 in DLP6500 reference circuit.

------------------------------

【Background】

・Reference schematic is attached.  (Page-3)

2511979B_LCR6500_DMDBOARD_P65_1080P_S600_CSTACK_FLEX_CONN (3).pdf
・Question point is R30, R34, and R38

【Question】

①If TPS65145 use on the maximum Iout of the spec,

  R30,R34,R38 will exceed maxim rating of Power Loss.

  (Ploss=I2R, these results were over 2W)

  Are these circuit no ploblem?

②I think that this reference made for low Iout case.

  (For example, SW:150mA, OUT3 and DRV:20mA)

  Is this thinking correct?

③If incorrect, please let me know about backgroound of

  "the reason of Resister value:No problem"

------------------------------

Best regards,

Satoshi

  • 0
    TI__Intellectual 2805 points

    Hello Satoshi,

    In these circuits, the current starts flowing in R3x when the power supply turns off until  the different output capacitors are discharged. This lasts a few milliseconds. Therefore the average power dissipated in these resistors is less than the power rating of 2W you gave.

    Best regards,

    Diaara

  • 0 in reply to Diaara
    Guru 19645 points

    Diaara-san

    Thank you for reply.

    Sorry for additinoal question about circuit of the other day.

    -----------------------------------------

    ・About TPS65145 output line (Voffset), page-5 connecting zener diode "BZD27C10P". 

    ・Is zener diode make protection circuit, is it correct?

    ・If correct, I think that zener diode can't protect perfectly.

    　・Reason

    　　BZD27C10P⇒VZ：9.4V～10.6V

    　　DLP6500⇒Voffset range：8.25V～8.75V (Maxim rating：9V)

    　⇒Protection can't because VZ > Voffset.

    　　Is zenerhave any other purpose?

    -----------------------------------------

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Mastermind 30875 points
    Hi Satoshi,
    We will check and let you know about the Zener diode selection.
    Regards,
    Sanjeev
  • 0 in reply to Sanjeev
    Guru 19645 points
    Sanjeev-san

    Thank you for reply.
    I look forward to your update.

    Best regards,
    Satoshi
  • 0 in reply to Satoshi
    TI__Mastermind 30875 points
    Hi Satoshi-san,

    Zener is meant for protection purpose only.

    Protection can't because VZ > Voffset;
    >> There is 9.4V - 8.75V = 0.65V of extra margin the device is exposed to; which is okay. If you look at the next lower-voltage Zener diode the operating range is 8.5V - 9.6V; this falls on the DMD operating range, we don't want the Zener diode to enter protection mode under normal DMD operating condition, this is the reason why we end up selecting higher voltage zener.

    Regards,
    Sanjeev