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TPS63030

Peyton C
Prodigy 175 points
Other Parts Discussed in Thread: TPS63030

I am using the TPS63030 for a buck-boost operation from a Li-ion battery.  Out put is set to 3.1V (approximate) using a 1.5M and 280k resistor divider.  My inductor is a 1.5uH (XFL4020-152meb) from coil craft. I have a 47uF electrolytic on the input in parallel with a 10uF ceramic.  On the output I have 2x10uF ceramic caps with a 470uF Electrolytic.  My VINA and Ven and Vsync are all tied together with a 0.1uF cap.  I have the ground on that cap and the resistor divider isolated from the power ground as is shown in the data sheet.  

My output voltage is correct and remains stable, however, my current draw at no load is 3.6mA.   where the data sheet shows it should be about 25uA which is what I need.  Is there something I'm missing to get the current draw down to micro-amp range?

Thank you!

  • 0
    TI__Expert 8420 points
    1. Could you post the schematic and layout of your circuit?
    2. I would also like to check the BOM, could you provide it?
    3. What is the purpose of this measurement? to check light load efficiency?
    4. How are you powering your board?
    5. How are you measuring the current?
    6.Could you exclude any soldering problem?
    In general electrolytic capacitors have higher leakage current, and you may have to wait some minutes before measuring the current
  • 0 in reply to Sabrina
    Prodigy 175 points

    Hey Sabrina, thanks for reaching out to help!

    1.) I don't see how to post an attachment.

    2.) In/out capacitors - 160R15X106KV4E , 10uF XR5 0805

         Inductor - XFL4020-152MEB

          VINA cap - GRM188R71C104KA01D , 0.1uF X7R 0603

         R1 - CRCW04021M50FKED , 1.5M 1% 0402

         R2 - ERJ-3EKF2803V , 280k 1% 0603

    3.) I need to make sure the converter isn't absorbing more power than is being generated.  We will have a base load of about 20uA @ 3.1V with a *** of 30mA every 10min or so.

    4.) The board is powered from a 500mAh Li-ion battery which is recharged through energy harvesting means.  Hence the need for the chip to be drawing in the uA and not the 3.6mA it currently is consuming at no load.  I've also tried powering the chip from a power supply.  I've tried adding more caps, and tried a variety of inductors.

    5.) I'm measuring the current through the positive connection of the battery using a 5.5 digit Agilent multimeter.  Also used a fluke 289 hand held meter.

    6.) I'm fairly confident it's not a soldering issue.  I've tried three different chips now.

    How long would you recommend waiting.  I had it connected several minutes and the current never changed.  When I added more electrolytic capacitance it would go up, but settle back to 3.6mA.

  • 0 in reply to Peyton C
    Prodigy 175 points
    The only thing I can think is that I have the PS pin pulled high. The data sheet says the Iq of the chip at no load is 25uA but they don't indicate what the state of the PS pin is (although the design example shows it tied high). To enable power save mode the PS pin should be tied low, but should this be a direct connection to ground or through a resistor?
  • 0 in reply to Peyton C
    Prodigy 175 points

    I made a new board, this time with the PS/SYNC pin grounded.  At first it was drawing 1mA but no output voltage was being generated.  If I put a fairly large output cap on the board it would ramp up to the set output voltage then drop back to zero.  I checked my solder connection again and this time that was the trouble.  The converter is now working, keeping a stable voltage at the output and drawing an average of about 25uA of current.