LM25011: LM25011 frequency

Rock Shao

Expert 2985 points

Part Number: LM25011
Other Parts Discussed in Thread: TPS54140A,

Hi,

Could LM25011 adj RT pin work at 130KHz?

Or can recommend other ICs for my customer, the needs as below, thanks.

1. Input voltage needs>40V.

2. output watt 12W (12V/1A).

3. frequency need fix at 130KHz.

4. OCP can release to 1.2A~1.5A.

Regards

Rock

over 4 years ago

0 Andy Chen over 4 years ago

TI__Mastermind 27355 points

Hi Shao,

Pls provide more application information:

1. Will customer accept 200KHz freq?

2. Does customer require the OCP adjustable?

LM25011 switching freq will varies with Vin or even load current.

B R

Andy

0 Rock Shao over 4 years ago in reply to Andy Chen

Expert 2985 points

Hi Andy

1. Will customers accept 200KHz freq?

The original design is 130KHZ, and the end customer didn't want to change, so needs 130KHz frequency for EMI consider.

2. Does the customer require the OCP adjustable?

The OCP needs under 1.5A. If the OCP inside the IC can be met, there is no need for an externally adjustable IC

regards

Rock

0 Andy Chen over 4 years ago in reply to Rock Shao

TI__Mastermind 27355 points

Hi Rock,

Please check TPS54140A which should meet your requirement.

B R

Andy

0 Rock Shao over 4 years ago in reply to Andy Chen

Expert 2985 points

Hi Andy,

I check TPS54140A the current limit is too high for customer application, The OCP needs under 1.5A.

Did you have other recommended? Thanks.

TPS54140A

0 Andy Chen over 4 years ago in reply to Rock Shao

TI__Mastermind 27355 points

Hi Rock,

Please download LM25011 Calculator for circuit design, Fsw=130KHz is OK and set Max load current to 1A~1.2A.

https://www.ti.com/tool/LM25011QUICK-CALC

B R

Andy

0 Rock Shao over 4 years ago in reply to Andy Chen

Expert 2985 points

Hi Andy,

Customer need to confirm LM25011 have output OVP, and output short protection function, thanks.

regards

Rock

0 Andy Chen over 4 years ago in reply to Rock Shao

TI__Mastermind 27355 points

Hi Rock,

LM25011 has PWRGD pin but only monitor output under voltage condition, no Over voltage protection.

it has output short protection by valley current limitation. customer should choice proper Rsense.

B R

Andy

0 Rock Shao over 4 years ago in reply to Andy Chen

Expert 2985 points

Hi Andy,

Thanks.

Could LM25011 add an external circuit to meet the OVP needs?

0 Andy Chen over 4 years ago in reply to Rock Shao

TI__Mastermind 27355 points

Hi Rock,

I think you may use voltage supervisor to monitor the output voltage, it should has OV and UV protection.

B R

Andy

0 Rock Shao over 4 years ago in reply to Andy Chen

Expert 2985 points

Hi Andy,

Did you have any reference design to used PGD to monitor the output voltage? thanks.

Regards

Rock

0 Andy Chen over 4 years ago in reply to Rock Shao

TI__Mastermind 27355 points

Hi Rock,

PGD is designed for output under voltage protection only.

below OVP circuit is suggested if customer don't care much about light load efficiency,

ZD1 is 13V 5% Zener diode, Rfb1=680~1K range.

B R

Andy

0 Rock Shao over 4 years ago in reply to Andy Chen

Expert 2985 points

Hi Andy,

My customer used LM25011MY-EVAL and add the OVP circuit,

but the high side Rfb2 will be broken when testing the OVP(shorting the low side Rfb1).

LM25011_Quick_Start_Calculator_30-32-Vin_12V-0.5A.xls

Rfb1 used 1KR(0603), Rfb2 used 3.9KR(0603)

Did you have another ideal for the OVP circuit? thanks.

0 Andy Chen over 4 years ago in reply to Rock Shao

TI__Mastermind 27355 points

Hi Rock,

FB pin will see 0V if short low side Rfb, this will definitely cause output over voltage which may close to input.

Send me email at andy.chen@ti.com for more information about OVP.

I will close this thread first.

B R

Andy

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LM25011: LM25011 frequency