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TPS61220 efficiency problem

BEN AMOR Hamdi
Prodigy 30 points
Other Parts Discussed in Thread: TPS61220

Hi,

Am trying to design a circuit powered from an 1.5V cell, i have chosen the TPS61220 to boost the 1.5V to 3V and am having some issues

first , applying recommended value of 4.7uH inductor made a huge output voltage drop, i tested some value , the only usable value for me is 100uH inductor and 470uF capacitor , otherwise i get terrible output wave form.

second with those values of L and output C, i get an efficiency between 30% to 50%

i tested with some pure resistive load and this is what i get

load 1K

Input current 12.5mA
Input voltage 1.5V

Output current 3mA
Output voltage 3V

Eff around 50%

load 250R

Input current 66mA
Outout current 12mA

Eff around 36%

The load i need the powerup with the TPS61220 is a BLE module most the time on sleep mode ( 300µA ) with pic current about 40mA when active.

I can't understand what am doing wrong, so any help please.

  • 0
    TI__Genius 10095 points

    Hi Ben,

    First off, I would recommend you repost this in the DC-DC forum; the Simple Switcher forum is for Simple Switcher branded parts and we don't have specific knowledge for the TPS61220.

    http://e2e.ti.com/support/power_management/non-isolated_dcdc/

    In regards to your question.

    You need to look at the inductor and output capacitors that you are choosing.  If you go back to your original 4.7uH inductor you said it had a huge output voltage drop.

    1) What was the DC resistance of this inductor?  How does this compare with the DC resistance of the 100uH inductor your picked?

    2) How about your output capacitors. You said that you had a horribleoutput waveform.  Are you like a 4.7uF ceramic output capacitor to keep the output voltageripple down?

    Regards,

    Marc

     

    1) Do you have some small cer

  • 0 in reply to Marc Davis-Marsh
    Prodigy 30 points
    sorry for this i will repost is DC/DC but i think it's already answered :D .
    i think you already said what i didn't think it would matter , well am using some generic component salvaged 4.7uH inductor and a 10uF electrolytic to test it in a prototyping board, didn't thought about using low DC resistance of the inductor and low ESR capacitor.
    I will test some proper components. Thanks.