TPS54233: Started with A load of 1.5A, but the output voltage is only about 2V

Tony xiong

Part Number: TPS54233

Hi Guy;

I have a problem; Started with A load of 1.5A, but the output voltage is only about 2V;Could you tell me what the problem is; thank you!

The following test was done;

1. It can be started normally under light load, and can work normally when the load is increased to 1.5a when the power is on;

2. After power supply, the switch between no load and loaded 1.5a can work normally;

3 if the defective board is replaced with a good IC, it can work normally and the undesirable phenomena will disappear;Replace again undesirable IC, phenomenon appears;The impedance of bad IC and good IC is almost the same.

4. Test the waveform of defective plates;Operating frequency: 300KHZ/8,Vsen< 0.2v;Comply with the characteristics of overcurrent protection described in the specification;Now suspect may be in the boot, IC overflow protection phenomenon

schematic diagram

over 4 years ago

0 Shawn Nie over 4 years ago

TI__Genius 10070 points

I can't see the schematic, could you please upload it again？Also, please share the layout and waveforms.

Shawn

0 Tony xiong over 4 years ago in reply to Shawn Nie

Intellectual 670 points

_Hi

add schematic diagram

add _

waveform

0 Tony xiong over 4 years ago in reply to Shawn Nie

Intellectual 670 points

schematic diagram and waveform.docx

0 Shawn Nie over 4 years ago in reply to Tony xiong

TI__Genius 10070 points

Hi,

You said if you changed the IC with a good one, there is no issue, right? Maybe the IC is damage.

The values of C16 and C18 are sthe same, this will lead to unstable, you can use Webench to do the simulation, and optimize the values of R38, C16 ,C18.

Shawn

0 Tony xiong over 4 years ago in reply to Shawn Nie

Intellectual 670 points

Start with only 1.5A Load, the output is abnormal . If the power has been on, switch between no load and load,

can work normally ; A bad IC has the same impedance as a good IC;I tried to change C18, and the bad phenomenon was the same;

0 Shawn Nie over 4 years ago in reply to Tony xiong

TI__Genius 10070 points

Hi,

Could you please share the layout? If the layout is not good, the board can't support large load current.

And please try to increase C16 to 2.2nF to check if there is any improvement.

L3 is a bead, right? Why do you add a bead here? Is it used to decrease the spike voltage of SW?

Shawn

0 Shawn Nie over 4 years ago in reply to Tony xiong

TI__Genius 10070 points

Hi,

Although the impedance of the bad IC and good IC are the same, but if there is no issue with the good IC, that is to say there is something wrong with the bad one, such as the internal logic circuit or MOSFET. If the Rdson of MOSFET is not correct, the OCP may be triggered incorrectly.

Shawn