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# LT3741 10V 20A power supply

Using the LT3741 fixed frequency synchronous step-down DC DC controller you can design power supplies applications that require a maximum current up to 20A. The LT3741 is manufactured by Linear technology and will maintain inductor current regulation over a wide output voltage range of 0V to (VIN – 2V). The LT3741 DC-DC controller IC operate over a wide input range , from 6 volts up to 36 volts . The regulated current is set by an analog voltage on the CTRL pins and an external sense resistor.

The switching frequency is programmable from 200kHz to 1MHz through an external resistor on the RT pin or through the use of the SYNC pin and an external clock signal.

The LT3741 has a very low shutdown current (
As you can see in this application circuit the L3741 support high output currents , this circuit will provide 10 volts output voltage and a maximum current of 20 amperes .

The analog voltage at the CTRL1 pin is buffered and produces a reference voltage, VCTRL, across an internal resistor. The regulated average inductor current is determined by:

IO =VCTRL1/(30xRs) where RS is the external sense resistor and IO is the average inductor current .

The maximum power dissipation in the resistor will be: PRS =[(0.05 )^2]Rs

Size the inductor to have approximately 30% peak-topeak ripple. The following equation sizes the inductor for best performance: L=(Vin x Vo- Vo^2)/(0.3 x fs x Io x Vin) where VO is the output voltage, IO is the maximum regulated current in the inductor and fS is the switching frequency .

The peak inductor current can be calculated using the following equation : Imax=Io+[(Vin x Vo- Vo^2)/(2 x fs x L x Vin)] where VIN is the input voltage, L is the inductance value, VO is the output voltage, IO is the regulated output current and fS is the switching frequency .

The regulated output voltage must be greater than 1.5V and is set by the equation: VOUT = 1.21(1+ R2/R1) .

The LT3741 has an operational switching frequency range between 200kHz and 1MHz that is programmed with an external resistor from the RT pin to ground.

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