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TPS55340-Q1: SEPIC Vin_min decreasing

Ivan Goncharov
Prodigy 120 points
Part Number: TPS55340-Q1
Other Parts Discussed in Thread: TPS55340

Hi team,

I'm using TPS55340-Q1 in SEPIC topology.

TPS55340-Q1 has 2.9V minimum input voltage. I'm going to use some bulk capacitance (polymer or maybe EDLC) to withstand input voltage dropout.

So it would be very useful if this SMPS could provide output voltage with Vin less than 2.9 volts (to use energy stored in bulk capacitors).

Please see attached schamatic. 

Whether the power supply will continue to work correctly if the input voltage falls below 2.9? Of course untill switch current does not exceed maximum value.

Thank you in advance.

  • 0
    TI__Guru 68435 points

    Hi Ivan,

    Thank you for considering the TPS55340.  Your idea should work as long as you keep VIN pin >2.9V, including startup.  Pay attention to the diode drop which may reduce the voltage at VIN pin to prevent it from starting up with a low VIN.  Once startup, your Vout can keep VIN pin voltage high, but your actual input voltage can be lower and the circuit will continue to maintain the output regulation until it hits either the peak current limit or max duty cycle.   

    Thanks,

    Youhao Xi, Applications Engineering