TPS7H4010-SEP: Does the PSPICE model included forced PWM mode?

first_name last_name

Part Number: TPS7H4010-SEP

Hello,

I've been running some simulations of the TPS7H4010-SEP, and for light loads I see the current enters discontinuous mode with an external sync signal present. Would this be expected in the simulation model?

My understanding is that with an external clock on the Sync pin the part is supposed to run in forced continuous.

In this example the synchronization is at 500khz, the inductor is 10uH, 77uF capacitance and a 150Ohm load. From the image it can be seen to be running discontinuously. You can also see the duty cycle bouncing around a bit in the switching waveform. (Note that a bit earlier in the simulation the current did actually go negative and looked a bit more like what I expected but then went into this mode in steady-state)

Do you think this part will be added to Webench anytime soon?

Thanks for the help!

Adam

over 2 years ago

0 Christian Yots over 2 years ago

TI__Genius 14540 points

Hi Adam,

I'm looping in our modeling expert to see if she has any ideas.

Thanks

Christian

0 Sarah Koch over 2 years ago

TI__Expert 7035 points

Hi Adam,

You're correct that the TPS7H4010-SEP goes into forced PWM model when the SYNC pin is tied to an external clock. I'm looking into whether this was incorporated into the model now and will update you here as soon as I have more information. Just in case it helps with debugging, can you post the schematic you are using?

Unfortunately it is unlikely this part will be added to Webench soon, as Webench is currently unable to provide space-grade component recommendations.

Thanks,

Sarah

0 first_name last_name over 2 years ago in reply to Sarah Koch

Prodigy 100 points

0 first_name last_name over 2 years ago in reply to first_name last_name

Prodigy 100 points

Thanks for looking into this! :) The image above shows my simulation. I was trying to get a second output at 30V using a coupled inductor at the same time as getting 15V. My understanding is that topology works better when the system remains in continuous mode hence I noticed the inductor current sitting at 0A

0 Sarah Koch over 2 years ago in reply to first_name last_name

TI__Expert 7035 points

No problem, thanks for letting us know about the issues you're encountering so we can improve our models!

I was able to replicate your simulation and see the same behavior and then lowered the load even further to 10mA to see how the inductor current would respond. It looks like the current is going negative like expected (meaning FPWM mode is included in the model), but there appears to be a brief window of time where the model is stalling out and we see oscillation at the SW node and plateauing of the inductor current at 0A.

I will need more time to look into what specifically is causing this behavior inside the model.

Thanks,

Sarah

0 Sarah Koch over 2 years ago in reply to Sarah Koch

TI__Expert 7035 points

Hi Adam,

Another update. The "stalling out" behavior only occurs in the model when using an external clock on the SYNC pin. If this pin is instead tied high (I connected it to VCC) the simulation shows the correct behavior.

This implies that the model was not built to be fully compatible with operating in FPWM mode when using a clock on the SYNC pin. I can continue looking for the specific issue with the SYNC pin circuitry inside the model and work on updating the model.

Thanks,

Sarah

0 first_name last_name over 2 years ago in reply to Sarah Koch

Prodigy 100 points

Thank you for your help with this. That's a good idea! I'll just tie it high (since I know the sync functionality works). Could you let me know when/if a new model becomes available :)

0 Sarah Koch over 2 years ago in reply to first_name last_name

TI__Expert 7035 points

Great, I'm glad this solution is at least sufficient for now. And yes, I will reply here if a revision of the model that addresses this is released so you receive a notification.

Thanks,

Sarah

0 first_name last_name over 2 years ago in reply to Sarah Koch

Prodigy 100 points

Thanks again! :)

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TPS7H4010-SEP: Does the PSPICE model included forced PWM mode?