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TPS72301 app quesions

Neil Li
Expert 7010 points


Regarding TPS72301, I have two questions:

1. When choosing the output capacitor, does this device have rules of  the capacitor volume and its ESR? As you know, some devices require ESR to be in special range, or else the loop is no stable.

2. If I want to add a small value cap at FB pin, another end of this cap should be connected at GND pin, correct?

Highly apprecicate your response! 

  • 0
    TI__Genius 15112 points

    1.  Please refer to Page 10. CAPACITOR SELECTION FOR STABILITY and OUTPUT NOISE section. Requires a 2.2uF ceramic output capacitor low ESR with additional 0.01 uF capacitor reduce noise.

    2. i had ever saw other device adding a small cap at FB pin. other end of this cap  connected to OUT pin. I do not know whether this device need this cap.

  • 0
    TI__Expert 3662 points

    Neil Li 说：

    Regarding TPS72301, I have two questions:

    1. When choosing the output capacitor, does this device have rules of  the capacitor volume and its ESR? As you know, some devices require ESR to be in special range, or else the loop is no stable.

    2. If I want to add a small value cap at FB pin, another end of this cap should be connected at GND pin, correct?

    Highly apprecicate your response! 

    Hi Neil,

    FYI.

    1. datasheet said it requre only 2.2uF output cap for loop stability. I checked the part number for 2.2uFV, 0805 ， ESR  is ~10mohm.

    http://psearch.murata.com.cn/capacitor/product/GCM188R70J225KE22%23.html

    For LDO, usually higher ESR result in more stability.

    2. Cap at FB pin, if it connect between Vout and FB, it provide a feedforward path, it will enlarge the bandwidth. please refer:

    http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slva466

    For Cap between FB and GND: it's the opersite of the upper contion, high frequency signal will bypass by the cap, so loop response will be slower.