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  • TI Thinks Resolved

LM25122-Q1: TIDA-00699

Genius 3225 points

Replies: 3

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Part Number: LM25122-Q1

Our customer consider to use LM25122-Q1 for their pre-boost circuit.

<Their specification>

Vin:8V~16V (surge 32V)

Vout:12V

Iout:2.3A

external sync:459KHz-488KHz

They refer to TIDA-00699 and modify R7(RFB2) to 90khms.

Is any other changing required? 

Please advise us.

 

http://www.tij.co.jp/jp/lit/ug/tidub49/tidub49.pdf

  • Thank you for considering the LM25122-Q1. I would recommend to change R11 instead of changing R7 to adjust the Vout, such that the loop compensation stays the same. I checked the Vout capacitors and the rating supports 12Vout. In short, it should work.
  • Genius 3225 points

    In reply to Youhao Xi:

    Youhao-san

    Thank you for your reply.

    We told that changing R11 is recommended to customer.

    We have additional questions.

    1.This part does't have EN pin. So they use UVLO pin for part ON/OFF
    Can they connect UVLO pin to MCU(3.3V) directly ?

    2.SYNCIN/RT
    In Master2 mode and they want SW frequency is 459KHz-488KHz,can they connect SYNCIN/RT to MCU(3.3V) directly ?
    MCU is external sync source :459KHz-488KHz

    3.
    Please let us know what purpose of D1 at Figure68 of TIDA-00699.
    Is this only for split rail low VIN operation ?

    www.tij.co.jp/.../tidub49.pdf


    regards,
  • In reply to kura:

    Kura-san,

    1.  Yes the UVLO can be controlled by MCU. 

    2. We recommend to insert a resistor between the pin and the MCU. 

    3. D1 is the ORing input for VIN.  It allows Vout to feed VIN during input battery cranking.  (see test report Figures 45 and 46)

    Thanks

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