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Low-cost, Wide-Input Buck Converter Options

Jim Gavin
Intellectual 920 points
Other Parts Discussed in Thread: TPS54040, TPS40200, TPS5401

The input parameters of the application are as follows:

Vin: 20-40V (it usually won't vary more than +/- a volt within each individual application, but it has to work across this range)

Vout: 5V

Vripple: +/-5%

Iout: 30mA - 400mA

The only constraints I have are cost, keeping audible noise to a minimum and keeping temperature rise minimized.  Efficiency is not critical as this is essentially this is the logical progression from just using a linear regulator, which will generate a lot of heat.

My original efforts went into using the MC34063 (MC33063), but I had issues with audible noise at the low end of the output current since the switch was actually only turning on at about 14kHz.  Ultimately, I'd like a faster MC34063 with feed-forward control based on Vin to keep a constant frequency over the input range.

 

  • 0
    TI__Guru**** 191445 points

    TPS5401 or TPS54040 would be the choices from the integrated FET family, but they are current mode.  TPS40200 is probably your best bet.

  • 0 in reply to JohnTucker
    Intellectual 920 points

    That's what I've narrowed it down to, but I am concerned about the TPS40200 operation at low output current (10-100mA).  The SwitherPro software doesn't even give the TPS40200 as an option when I give it a minimum current of 0.04A and shows its minimum current at 100mA.

    Any major distinctions between the TPS40200 and TPS5401 that might help make the decision?  I think cost might come to a wash with the external components needed for the TPS40200.