WEBENCH® Tools/TPS54335A: Failure for 90% duty simulation

Satoshi

Guru 19495 points

Part Number: TPS54335A
Other Parts Discussed in Thread: TPS54334, TPS54334EVM-722

Tool/software: WEBENCH® Design Tools

I simulated TPS54335A's Webench on below condition, but failure and indicate "Calculated duty cycle exceeds limit" .

I think that TPS54335A Webench data have a bug because I tried Low fsw condition but same results, please confirm it.

If it was bug, please let me know about revision schedule.

・Vin： 13.2V～21V

・Vout： 12V

・Iout： 1.1A

【Additional information】

・When fsw is changed low value (100kHz, 500kHz, etc), results was the same (duty cycle exceeds limit).

・TPS54335A datasheet is described "Min off time： 0%"

・TPS54334 was simulate normally, I feel that TPS54334 and TPS54335A are near specification.

Best regards,

Satoshi

over 6 years ago

0 Gerold Dhanabalan - Online Design Tools over 6 years ago

TI__Genius 14455 points

Hi Satoshi,
We are looking into this. We will get back shortly.

Regards,
Gerold

0 Satoshi over 6 years ago in reply to Gerold Dhanabalan - Online Design Tools

Guru 19495 points

Gerold-san

Thank you for quick reply.
I looking forward your update.

Best regards,
Satoshi

0 Ryan Hu (BSR-MV) over 6 years ago in reply to Satoshi

TI__Expert 4035 points

Hi Satoshi-san,

The TPS54335A/336A could support 100% duty cycle as long as the Boot cap voltage higher than 2.1V, when the voltage lower than 2.1V, device will turn off the high side fet, and turn on the low side fet to charge the boot cap, but the charging time is very short. on webench we limited the Max duty cycle on account of the charging time and the voltage drop on semiconductor i think. For your reference, i attach the actual test data on TI EVM below:

TPS54335A
Vin(V)	Iin(A)	Vout(V)	Io(A)	Min-off time(ns)	Note
12.69	2.990	11.91	2.990	50ns	Vin_min for 12V/3A output
11.0	2.990	10.2	2.990	121.6	10.2V/3A output for 11V input situation

BRs,

Ryan

0 Satoshi over 6 years ago in reply to Ryan Hu (BSR-MV)

Guru 19495 points

Ryan-san

Thank you for reply.

Sorry for additional question;

In the same condition(13.2Vin_min), TPS54334 is simulated normally.

I think that TPS54334 and TPS54335A are very nearly spec device.

Are these device different for internal circuit?

Best regards,

Satoshi

0 Ryan Hu (BSR-MV) over 6 years ago in reply to Satoshi

TI__Expert 4035 points

Satoshi-san,

The version of TPS54335A has been updated, the new version support 100% Duty cycle. I think the reason (but not 100% sure) is that we didn't update the webench data since the changes is very small and make no big difference.

BRs,
Ryan

0 Satoshi over 6 years ago in reply to Ryan Hu (BSR-MV)

Guru 19495 points

Ryan-san

Thank you for update,

Please let me check about one point below for test data by you attached.
About test data, What is TI EVM ?
I think that it is based on TPS54334EVM-722 and replace TPS54335A, is it correct?

Best regards,
Satoshi

0 Ryan Hu (BSR-MV) over 6 years ago in reply to Satoshi

TI__Expert 4035 points

Hi Satoshi,

Test based on TPS54335A EVM, which is going to be released soon. Tested on what's kind of EVM is not the main point, the main point is that TPS54335A could support 100% duty cycle working.

BRs,
Ryan

0 Satoshi over 6 years ago in reply to Ryan Hu (BSR-MV)

Guru 19495 points

Ryan-san

Thank you for good news, I interested in TPS54335A EVM.

About your test data, what condition for switching frequency?
(TPS54335A is adjustable)

Best regards,
Satoshi

0 Ryan Hu (BSR-MV) over 6 years ago in reply to Satoshi

TI__Expert 4035 points

Satoshi-san,

The RT resistance is 143kohm and the Switching frequency is 340kHz.

BRs,

Ryan

0 Ryan Hu (BSR-MV) over 6 years ago

TI__Expert 4035 points

To all Users,

Make a clarification here.

Neither TPS54335a nor TPS54334 could support 100% duty continuously, the so call 100% duty operation is based on Transient response, where the HSF could be turn on for several or even tens of clock cycles if Boot cap voltage is high enough..
But we can’t use this to calculate the output input voltage relation. 90% maximum duty is a reasonable value to use here.

Ryan.

Simulation, hardware & system design tools

Simulation, hardware & system design tools forum

WEBENCH® Tools/TPS54335A: Failure for 90% duty simulation