Buck DC-DC converter ICs, with internal MOSFET and freewheeling diode ???

Discussion in 'The Projects Forum' started by esm., Mar 11, 2012.

  1. esm.

    Thread Starter Member

    Jan 20, 2012
    I am looking for a buck converter IC available in a small SMD package like SOT-23 (or other small one) to a power supply with these parameters:

    Vin = 16 to 30VDC
    Vout = 4.4VDC
    Iout = 250mA

    The maximum output peak current is also 250mA. The 4,4V rail will be used to supply voltage to a constant current supply (to a Li-Ion battery charge management IC). If possible, a higher output current capability would be better, but 250mA is enough for me.

    It would be much better a buck converter IC who meet the parameters above and doesn't require the use an external MOSFET and also not require an external freewheeling diode. I didn't found.

    I'm using TPS63000 from Texas Instruments in some designs. It is a buck-boost converter that doesn't need an external MOSFET nor an external freewheeling diode when operates in buck mode.

    I have many 1A SMD inductors with values from 4.7uH to 68uH. I just need to define which IC to be used. If don't find an IC who meet the parameters above, I will need to use a LM2596-ADJ buck converter from National Semiconductors to do the buck conversion, but it requires much more PCB space than the IC I am looking for.

    Somebody know some good ICs to meet the parameters above?
    Preferentially, ICs that doesn't require external MOSFET, freewheeling diode and is availabe in a small SMD package like SOT-23.

    Or some other suggestions of ICs with bigger size package that doesn't require external MOSFET nor a freewheeling diode ????
  2. DickCappels


    Aug 21, 2008
    The MC34063 can be used that way. It is available in an SOIC 8 package. It is bipolar and the output is a Darlington pair, so there is some unavoidable loss there, but it should not have any problem with your current at the 16:4 voltage ratio. I would need an external free wheeling diode when used in a buck configuration, but it would be a small diode.
  3. John P

    AAC Fanatic!

    Oct 14, 2008
    The MAX1837 matches your criteria except that it needs an external diode.

    Have you tried Linear Technology?
  4. shortbus


    Sep 30, 2009