WEBENCH® Tools/TPS62822: Simulation

KEERTHANA S67

Prodigy 150 points

Part Number: TPS62822
Other Parts Discussed in Thread: TPS62800, TPS6283810, TPS62825,

Tool/software: WEBENCH® Design Tools

3.3V to 1V-500mA.docx

I have simulated TPS62822DLCR in Webench.

Please find the attached simulation report.

I am getting a spike in waveform while doing start up simulation. May I know, why we are getting this spike?

over 5 years ago

0 Harish K R over 5 years ago

TI__Intellectual 2320 points

Hi Keerthana,

Initial Spike in Vout during startup is expected as the device works in PSM (Power Save mode) mode. Also, the on time initially will be limited by device minimum on time which will result in small spike in Vout. Please find below snapshot of data-sheet FYR.

In general, for buck topology on time can be estimated as Vout/(Vin * frequency)

During initial ramp up, Vout will be very small which will result into very small calculated on time. But due to minimum on time limitation of the device, the actual on time would be higher. This will result into spike in Vout initially.

Kindly let us know in case of any queries

Thanks & Regards,

Harish

0 Chris Glaser over 5 years ago

TI__Guru*** 147360 points

Hi Keerthana,

This looks to be a misunderstanding in the model. You can see from the D/S, figure 39, that there is no such spike in Vout at startup.

The on time equation is for steady state and not startup conditions.

As well, if you need a smaller size we have TPS62825, TPS6283810, and the tiniest TPS62800.

Harish, can you check with the model approver on this behavior?

0 Umayal Ramanathan over 5 years ago in reply to Chris Glaser

TI__Expert 5230 points

Hi Chris,

Apologies for the delay. We are working to identify the reason for spike during start up in TPS62822.

We shall keep you updated on the same.

Thanks & Regards,

Umayal

0 KEERTHANA S67 over 5 years ago in reply to Umayal Ramanathan

Prodigy 150 points

Hi Umayal,

Awaiting for your reply.

Regards,

Keerthana S

0 Umayal Ramanathan over 5 years ago in reply to KEERTHANA S67

TI__Expert 5230 points

Hi Keerthana,

We apologize for the delay in response. Corresponding team is debugging the reason for initial spike during start up.

We shall get back to you on the same.

Thanks and Regards,

Umayal

0 KEERTHANA S67 over 5 years ago in reply to Harish K R

Prodigy 150 points

5V to 3.3V-2A.docx

Hi Harish,

Thank you for your reply.

I have simulated for both less load and high load in the range of 100mA and 2A. But I am getting a spike in both loads. The device will be using for 2A conditions, but in some cases it may go below 100mA. So that we have did simulation for both high and low loads.

Attached simulation report for 2A also. Please check why we are getting a spike?

0 Harish K R over 5 years ago in reply to KEERTHANA S67

TI__Intellectual 2320 points

Hi Keerthana,

Thanks for providing report for 2A.

The concerned team is looking into your query. Team shall get back to you on the reason for spike in Vout during initial phase of startup.

Thanks & Regards,

Harish

0 KEERTHANA S67 over 5 years ago in reply to Harish K R

Prodigy 150 points

Hi Harish,

Thank you.

Expecting your reply at the earliest.

Regards,

Keerthana S

0 Harish K R over 5 years ago in reply to KEERTHANA S67

TI__Intellectual 2320 points

Hi Keerthana,

There is an issue w.r.t WEBENCH model which is why you are observing higher spikes initially during startup. As mentioned by Chris in his reply, there is no spike observed in measured results (as per Data-sheet fig 39)

We configured similar test-bench as WEBENCH [Vin = 3.3V, Vout = 1V at 0.5A] in standalone PSPICE model and the Vout ripple is lesser (40mV only) as compared to WEBENCH results.

Kindly use standalone PSPICE model which is available at below location and let us know in case you have further queries.

http://www.ti.com/product/TPS62822/toolssoftware

Thanks & Regards,

Harish

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WEBENCH® Tools/TPS62822: Simulation