TPS63000-Q1: Very high current consumption

Hi  Arild,

without any delay, TPS63000 will start-up as soon as  input voltage is larger than UVLO point(close to 1.8V). then input voltage  will be pulled down and tps63000 shunt down. Repeatedly work in this state.

in your application, power save mode is disabled. so TPS63000 will try to discharge output cap at the beginning of start-up for there is a bias-voltage at output and output never be builded up compeletly.

so, an option is add a RC net between VIn and EN to make sure TPS63000 start to work when input voltage is builded up already.

Regards

Tao

Thanks Tao,

It's very difficult (impossible) to add a delay to the EN pin without making a new PCB layout. I therefore tried changing the inductor from 2.2uH to 10uH, and now it works!. The increased inductance seems to fix the problem. Maybe the original inductance was slightly lower than 2.2uH. My LCR meter shows 2.0uH, but I don't know how accurate this instrument is.

Regards

Arild

Hi   Arild,

interesting, i never think increasing inductance will help to fix this issue, good job.

BTW, did you change your cable between power source and your board?

it will impact your test results. And make sure the change of efficiency and transient performance are acceptable.

if possible, you can increase your input cap to increse your margin too. 

Regards

Tao

Hi,

I changed the inductor to 4.7uH on 8 boards, and 7 of them seems to work ok now.

The boards with failure were tested with 3 different computers as power supply, with three different USB cables.  I got the same problem when using a lab power supply with wires soldered directly to the PCB.

I will try increasing the input capacitance. That will be an interesting test.

Regard

Arild

Hi Arild,

hope it will help. wait for your update.

Regards

Tao

Hi Tao,

I placed a 1000uF capacitor at the input, but it didn't help very much. It started a couple of times, but most of the times it will not start with a 2.2uH inductor. Changing the inductor to 4.7uH seems to help. It seems to start every time.

Regards

Arild

Hi  Arild.

that is really strange, i think devise restart repeatedly in your orginal test for UVLO trigged and a larger input cap will help.

it is good that you have a solution already.

Regards

Tao