Hi Muhammad Usman,

Please fill in the quickstart calculator for this device: https://www.ti.com/tool/LM5149-LM25149DESIGN-CALC and also share the schematic with me.

Furthermore, if you are planning a 12-32V step down to 5V with 5A of output current - I would recommend you use a device with an integrated FET - it will be a cheaper and simpler implementation when compared with a design with external FETs (which is mostly recommended for higher output power designs). 

Please look at https://www.ti.com/product/LMR51450 and  www.ti.com/.../LM62460

Thanks,

Best Regards,

Taru

Hi, Thanks for quick response. I have already used the webnech-circuit designer and all componensta and circuit acording to the design provided by Texas Instrumentation 

I need 10A with MAX input of 44VDC of current and the chip LM62460 is only have 6A of current can you suggest for 10A at 5A with input of 44VDC ?
Design files are attchecd(Altium Designer) and PDF.

7624.PCB Sentry Gun Beta Version 1-JUL-2025.zip

Hi Usman,

Muhammad Usman said:

I have already used the webnech-circuit designer and all componensta and circuit acording to the design provided by Texas Instrumentation

Understood - however, the loop response will depend on the passives that you have used - the DC bias derating and other stuff will play a role. It is also easier for me to review based on the design calculator.

I see some issues already with the design:

1. You mentioned fsw = 440kHz - which requires Rt of 49.3kOhm. 21kOhm leads to 1MHz of fsw. 

2. For Sense resistance of 5mOhm with your specs - current limit setpoint is 11.8A - we recommend the setpoint to be ~140% of Max current. 

Hence, I would like to request you again to fill in the calculator and share with me.

Muhammad Usman said:

I need 10A with MAX input of 44VDC of current and the chip LM62460 is only have 6A of current can you suggest for 10A at 5A with input of 44VDC ?

I suggested those devices since you mentioned 5A at 12–32 V input to 5 V output. Please confirm your requirements. 

Even with 44V Vin support for 10A out at 5V - you can check out www.ti.com/.../LM706A0.

Thanks,

Best Regards,

Taru

Sorry for inconvience basically these are tested Volatges and at these Voltages the Mosfet Burns and that;s whay I can not go at high Voltages.

1: I have used the same values and Schematic as given by online Design Tool(Webnech Designer).
2. Sensr resistor is also given by Texas Instrumentation .

Here is Reference design which I have got from Texas Instrumentation from online Tool.WBSchematicLM5149RGYR.zip

Hi Muhammad,

1. Please share the WEBENCH files. 

2. You need to fill in the calculator based on your schematic and not the actual test data. I have tried to fill it by myself based on your schematic - please check and let me know if those are the specs you are going after? 

LM5149 Quickstart Calculator Muhammad Usman.xlsm

Comments that I need from you about your design:

a. Confirm the switching frequency.

b. Confirm the max current of your design. Based on the above - select sense resistor. Current resistor value is quite high. 

c. Confirm the inductor DCR. 

d. Confirm the DC Bias derated values of output capacitance and the ESR. 

e. Input capacitor is very low. 

3. What is the input source to your design? 

4. LM5149 has Active EMI Filter - Since you are not using this - I would recommend you select LM5148

5. Do you have any scope captures from the testing that you have done? If yes, please share. 

6. I see the name of the project as 'Sentry Gun' - is this a defense/ military project? 

Thanks,

Best Regards,

Taru

Muhammad Usman said:

Here is Reference design which I have got from Texas Instrumentation from online Too

This is just the schematic - what are the specs that you filled in. Kindly share the entire design. 

I already see some discrepancies between this design and your design. The Rt in the WEBENCH design is 30kOhm which sets the switching frequency at around 700kHz - your design is at 1MHz. The output caps, input caps and the inductors are also different.

1) I have captutred the schematic by putting parameter in webnech Power Designer. Files are attached.
2) Perfect. All are okay.

a. 1000KHz
b. Max Current 10A
c. 5.4mOhm Max 
d.GRM32EC81C476KE15K has X6S Dielectric
e. Used same No of capacitor as given by Webnech Power Designer

3. Battery and tested it on Stable Power Supply as well
4. Noted. Do you think this will resolve the issue?
5. Yes. Attached.
6. No it's just a name.

Thanks for your cooperation and patienceScope.zipDesign Webnech Power Designer.zip

Noted. But these values only change performace but why MOSFET is burned and not Giving Stable voltage?

Hello

Hello Taru Kapoor How long will it take?

Hi Usman,

I'll get back to you by EoD. 

Thanks,

Best Regards,

Taru

Hi Usman,

Apologies for the delay!

Please see my comments:

Muhammad Usman said:

1) I have captutred the schematic by putting parameter in webnech Power Designer. Files are attached.

As before, this is just the schematic. Please see how to export a WEBENCH design below:

Go to the top right of the WEBENCH Window and click on Export:

Click on the share design option:

Use the Public Link Option and create a link to your design:
\\

Muhammad Usman said:

4. Noted. Do you think this will resolve the issue?

This is to improve your design - if you are not using a feature of the device - you can move to a simpler device. 

Taru Kapoor said:

5. Do you have any scope captures from the testing that you have done? If yes, please share. 

The waveforms that you have shared - do they show the Switch Node? Or the output voltage? 

Please send zoomed in waveforms - there's not much I can tell from the captures. 

Thanks,

Best Regards,

Taru

These are output waveforms

Hi,

Muhammad Usman said:

output waveforms

Output Voltage? 

If yes - this doesn't look right - Increase output capacitors as recommended and check response.

Meanwhile, please share the WEBENCH design that you used (I have outlined the steps for you).

Thanks,

Best Regards,

Taru

Outout voltages are 5V. Already checked by increasing the Output Capacitors. Please note that I have already shared a WEBNECH Design. Again attached please see WBBOMDesign13.csv

Hi Muhammad Usman,

I have sent you a friend request - please share your email address there - I believe it will be better if we can communicate over email and close this. 

Thanks,

Best Regards,

Taru

Hi,
mu452@yahoo.com 

Sure