TPS61027 Output current = Input current

Hi Ejoub,

Thanks for your sharing.

When you put a solenoid at the output, how much was the value of output voltage? 

How much is the DCR of the 6.8uH inductance?

I wonder if the output is so lower than input ( 3 V ), which keeps the TPS61027 in Precharge stage.

Regards,

Jason

hi Ejoub
what is the resistor of the Solenoid?
please startup the TPS61027 first, then connect the solenoid. if the device startup with the connection of solenoid, the device could be always at pre-charge stage if the resistor is low.

thanks
Jasper Li

Hi Jason,
When I put the solenoid at the output, the output voltage falls to about 2.8V.
The DCR of inductance ist 0.1 ohm

Regards
Ejoub

Hi Jasper Li,
the resistor of the solenoid is 54 ohm.
I started it up first without the solenoid, but that brings no changes.

Thanks
Ejoub

Ejoub
please capture the VIN and VOUT voltage (measure close to the PIN) at the time you connect the solenoid. so i can know what happen.

what is the part number of your inductor?

thanks
Jasper Li

Hi Jasper Li
I will make some pictures, and the part number is: 744 778 500 6 from WE Würth Elektronik
6.8µH; 2.3A; 0.1ohm

thanks
Ejoub

Hi Jasper Li,

here are the pictures.

VOUT not connected to the solenoid

VOUT connected to solenoid

VBAT with VOUT not connected to solenoid

VBAT with VOUT connected to solenoid

I hope that will help

Thanks a lot

Ejoub

Hi Ejoub,

Please capture the transient waveform at the very time you change the load. 

Thanks.

Jason

Hi

I made two pictures of VOUT

without connection

with connection to solenoid 

I hope this helps

Thanks a lot

Regards Ejoub

hi 

why there is ringing in the output waveform?

could you also capture the VIN and VOUT at the same figure.

and i want to have the waveform at the moment that the solenoid is connected, NOT after the connection . (i would expect the VIN and VOUT drop down when the load is connected)

please also share the PCB layout

thanks

Jasper Li

Hello,

I don't have a PCB Layout, I have to make it work before I can do one.

Last friday it worked on a breadoard and breakoutboards. This time I put the TPS in oven for 24 hours before I soldered it.

But it just worked to 2.1 V Input and at the same time it, doesn't work again.

Do you think that with a PCB the problems will be gone?

Regards

Ejoub

hi Ejoub
how many TPS61027 have you put in the oven? does they all fail? what is the temperature of the oven?

how the device hehaves when fail, does its SW pin short to GND?

DC/DC power converter is sensitive to layout. i would suggest do a real PCB to evaluate it. or you can apply an EVM.

Thanks
Jasper Li

Hi Jasper

I put the last one, an this one which worked with 5 V at the output, but not with connection to the solenoid. The oven is 100°C hot.

The SW pin is near to GND. The input current is sometimes high enough to get the solenoid work but at the output it doesn't arrive.

It get hot when the input is connected but there is no load, when I connect the solenoid it keeps cool.

Is it a characteristic of the device, that it gets hot when there is no load connected?

Thanks

Ejoub

the device only become hot when it causes large power loss .
i guess the device is damage, as the SW pin and GND should be high impedance. it is not caused by oven which is only 100 degree, much lower than the storage temperature 150oC.

thanks
Jasper Li

Hi

I wrote last week but something gone wrong, so the message doens't send.

After I put it in the oven at 100°C, can I put it, to solder it, in the oven at 245°C for 30 seconds?

And I need to know, is the device developed to have no load? I mean, can I have a input voltage but the at the output is no load?

Thanks

Ejoub

hi Ejoub
i think it is ok to put it in 245 degree for 30 Seconds. please refer "SLUA271A" page 14 for solder the device.

this device support no load operation, it will operates at PSM.

thanks
Jasper Li