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LM25119: Designing a converter

user6055494
Prodigy 30 points
Part Number: LM25119


hello,

LM25119

i m planning to design a converter with parameters below:

Vin: 28V
Vout: 25V
Iout: 25A (can be set by external sources to 20A or 15A or 10A)

with this controller and its application circuit.
how can i add output current setting option without changing any hardware?
is it possible to set output current with adding some voltage to ramp pin? as i read from datasheet, output current set is depended on 2 things, 1. Cs pin (Sample and
Hold DC Level) and ramp slope.
for me it is not possible to add some slope externally but i can add some DC level to this pin. is it useless? or any other idea?
the point is, users could be able to set output current to those values mentioned above via software (software will change this level on ramp pin?)

Apart from that, can I use any other component for this kind of application.

  • 0
    TI__Mastermind 24075 points

    Hello, 

    If Vout is fixed at 25V, the actual Iout is decided by the load, not by converter. 

    With Vin=28V and Vout=25V, the duty circle is larger than 0.9. 

    If LM25119 is used for this application, the switching frequency should be low such as 150kHz,  otherwise the duty circle will be limited and Vout can not be regulated. 

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Prodigy 30 points

    I guess you have no idea about 'current limitation'.

  • 0 in reply to user6055494
    TI__Mastermind 24075 points

    Usually Iout stand for output current. 

    If Iout means current limit in your question, you should make it clear, understand?

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Prodigy 30 points

    let me explain clearly,

    i already have a converter with max 20A output and planning to design a converter up to 30A independent from output load (if load impdeance is lower than required max output voltage).

    Iout is output current and its maximum value should be set by controller not by load even for short circut situtation. (user defined e.g. tti power supplies)

    if it was that easy like you said, i would not be asking for external current limitation setting. 

    while i was asking for ramps or other detailed features, why are you keeping this conversation as beginners?

    Thanks.

    Çağlar

  • 0 in reply to user6055494
    TI__Mastermind 24075 points

    Hello, 

    I have no idea how to adjust over current limit without hardware change for this part. 

    Would suggest to consider other part. 

    Sorry about it. 

    Thanks

    Qian