TPS74401 Output noise

Sneha Kumari

Other Parts Discussed in Thread: TPS54425, TINA-TI, TPS74401

Hi,

I am trying to simulate the power supply using Tina-Ti. 12V input is applied to TPS54425 DC-DC, its output is 4V. This 4V is the input to TPS74401. Output is 2.5V. At higher loads there is noise in the output of TPS74401. I tried with different load currents, above 500mA load there is noise in the output. SS capacitor of TPS74401, I tried different values. Still no change. Could anyone please comment on this?

Waveform is attached for your reference. SS capacitor used is 300pF.

regards,

Sneha

over 10 years ago

0 Britt Brooks - Online Design Tools over 10 years ago

TI__Mastermind 41310 points

Sneda,

The same issue has already been posted. Please see the following post:

https://e2e.ti.com/support/development_tools/webench_design_center/f/234/t/417769

I do not have a solution yet for the issue. I do not believe that the noise is real. I believe it is a simulation artifact.

0 Sneha Kumari over 10 years ago in reply to Britt Brooks - Online Design Tools

Intellectual 320 points

Dear Britt,

Thank you very much.

It seems TPS74401 PSRR is the cause for noise at output. TPS54425 output contains a 700Khz,10mV noise. When I applied a voltage source with same kind of noise as input to TPS74401, simulation output contains noise. At 400Khz, there is no output noise, I got it from 600KHz onwards at high load (tried with 2A,4.7uF output capacitor). At 100mA load, no problem with the output. Still the level of output noise getting in simulation is high.

regards,

Sneha

0 Britt Brooks - Online Design Tools over 10 years ago in reply to Sneha Kumari

TI__Mastermind 41310 points

Sneda,

That may well be part of the issue with the model, however, we did release an updated model for PSpice and the TINA-TI model was not updated. I am attaching the unencrypted PSpice model to this post.

7612.TPS74401_TRANS.lib

Please follow the directions below to import the model into TINA-TI. Please note that the new model has a different number of pins than the previous model, so you will need to adjust your schematic accordingly. I apologize for the inconvenience and delay.

https://e2e.ti.com/support/development_tools/webench_design_center/w/faq/3059.importing-unencrypted-pspice-models-into-tina-ti

The updated model should eliminate the noise issue.

Simulation, hardware & system design tools

Simulation, hardware & system design tools forum

TPS74401 Output noise