Author Topic: TPS63001 voltage drop under load  (Read 435 times)

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Offline Lt_Flash

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TPS63001 voltage drop under load
« on: April 25, 2018, 06:49:34 am »
Hi everyone,
I've created a simple board that uses a fixed output 3.3V TPS63001 switch mode regulator. According to the datasheet, I've chosen a 2.8A shielded wire-wound inductor (TDK SPM-LR Series Type 3015 Shielded Wire-wound SMD Inductor with a Metal Core, 2.2 μH Wire-Wound 2.8A Idc, RS Australia stock number 123-3132), input capacitors are 10uF and 100nF, output ones are two 10uF ones, size is 0805. The issue I'm having is that if I connect even one 6.8Ohm 5W resistor - I'm getting a voltage drop on output of about 300-500mV, if I connect two 6.8Ohm resistor to ramp up current to about 1A - I'm getting only about 3.1V output. Input is connected to a lab power supply set to 3.7V and 1.5A of output. On lab power supply I can see that it stays in CV mode and consumption current is about 0.95A-1.1A. I'm measuring output directly at wires connected to resistor(s). According to TPS63001 datasheet output should stay stable at 3.3V up to 1.2A of current supposing input stays at or above 3.6V. Am I doing something wrong in measuring this or there can be something else? Thanks a lot for your help in advance!

P.S. I don't have an oscilloscope at the moment, but ordered one to see what's going on inductor and output pins. Maybe inductor is not beefy enough? 2.8A should be sufficient though.
 

Offline Lt_Flash

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Re: TPS63001 voltage drop under load
« Reply #1 on: April 28, 2018, 09:06:03 am »
Just to answer this question for anyone who has same problem - well, I've just got another confirmation that electrical enginnering is a science all about contacts :) I was measuring voltage on 6.8Ohm resistor connected to a breadboard with dupont wires. And of course, there was a huge voltage drop due to high current of about 1A over these wires and breadboard contacts/tracks. So, after connecting resistor directly to regulator output I've got a constant 3.3V all the way up to 1.2Amps - as per datasheet. Also I've finally got my oscilloscope and even measured noise - it's less than 100mV under full load, so I'm finally quite happy with my design! Anyone interested please feel free to have a look at design and description here (all the release files are included on that page, including Gerber, schematic and PCB board layout files).

https://workspace.circuitmaker.com/Projects/Details/LtFlash/Sandwich-Regulator-board


« Last Edit: April 28, 2018, 09:15:54 am by Lt_Flash »
 


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