TPS5430 - Oscillation during power up

Soundarrajan Karuppusamy

Other Parts Discussed in Thread: TPS5430

Hi,

I am using TPS5430DDA in my application. I am observing some oscillation during power up. Below are the input and output parameters of my design. I have attached the waveform captured for reference. What is the reason for the oscillation and how to avoid it. Also one 4.7mF capacitor along with 0.1 Ohm series resistor need to be added in the input for power holdup purpose. Please let me know whether this addition will impact the performance.

Input voltage: 28V

Output voltage: 5.25V

Actual Load: 1.2A

430uF Aluminium capacitor is used at output and compensation network values are C=0.027uF and R=309 Ohm.

Regards,

Soundarrajan K

over 14 years ago

0 JohnTucker over 14 years ago

TI__Guru**** 191445 points

I need to see your complete schematic. Also can you take some waveforms showing the PH node?

0 Soundarrajan Karuppusamy over 14 years ago in reply to JohnTucker

Prodigy 70 points

Hi,

I have attached the full Schematic of TPS5430. I have designed the power supply in a daughter card and this daughter card will be mounted on a Main PCB. The Main PCB is haviing single 4.7mF holdup capacitor with 100mOhm series resistor at input (28V) and 330uF aluminium capacitor along with 2 number of 10uF ceramic capacitors at output (5.25V).

Regards,

Soundarrajan K

TPS5430 SCHEMATIC.pdf

0 Soundarrajan Karuppusamy over 14 years ago in reply to Soundarrajan Karuppusamy

Prodigy 70 points

Please find the attached waveform capturd in PH node where the oscillations present in 5.25V ouput supply during power up.

0 JohnTucker over 14 years ago in reply to Soundarrajan Karuppusamy

TI__Guru**** 191445 points

If CH32 is vout and CH3 is PH then there are no correlation between the change in output voltage and switching frequency. Please try to post any waveforms that show a correlation between your output voltage variation. I would especially be interested in PH during your start up sequence. Try to trigger on output voltage change rising or falling edge. Also you could try isolating the output of the converter from your load and powering just into a resisitive load.

It is difficult to troubleshoot over the forum. You may need to get your local AFA to have a look at your circuit.

0 JohnTucker over 14 years ago in reply to Soundarrajan Karuppusamy

TI__Guru**** 191445 points

If you have 330 uF additional capacitance at the load, you may have problems. Try the TPS5430 circuit using just the daughter card and apply 28 V directly and look at the output. Also I need to no the type and part numbers of the AL electrolytics.

Power management

Power management forum

TPS5430 - Oscillation during power up