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TPS61027: Unable to maintain 5V output @ 200 ma with 2V input, using reference circuit from data sheet

Bob Funk
Prodigy 10 points
Part Number: TPS61027

 

Name size / pkg tc / tol / source Part ID
10 uF 6.3V 0603 X5R 10% Murata GRM188R60J106KE47D C7
100 uF 10V 2312 tantalum 20% 75mOhm AVX TPSC107M010R0075 C6
2.2 uF 10V 0603 0603 X5R 10% Murata   GRM188R61A225KE34D  C8
6.8 uH 1.5A n/s SMT 6.8 uH shielded 1.65A 50mOhm EPCOS B82462G4682M L1
TPS61027 10-VFDFN TI TPS61027DRCR U3

The device starts OK with 2.5 v input and 5v output.  When the load current increases to 200 mA, the output voltage starts to drop, and continues to sag to about 3 volts with 300 mA load current.

I have tried adding 100 uF ceramic cap directly from pin 6 to ground, and changing C6 to a higher ESR part (47 uF 1 ohm).  Behavior changes but does not improve.

back side of PCB is solid ground plane (Green in layout view).

What can be done to stabilize the output with higher currents?  Changing to a different part at this point would be "awkward".  I need to source 400 mA at 5V output reliably, with Vin between 1.5 and 5.5 volts.

Thanks for any advice you can offer.

  • 0
    TI__Mastermind 46905 points
    Could you upload the schematic and layout again. i can't see them.
    please also measure the waveform of VOUT, VIN and SW pin at 200mA condition.

    this device can't support 1.5V input, 5V & 400mA, it will trigger current limit. and as the input voltage 5.5V can be always higher than the output voltage 5V, i would suggest you select a buck-boost converter, instead of boost converter.