LMR14050SEVM: LMR14050SEVM output 5V, 4A at 7V input

Prabhat Kumar31

Part Number: LMR14050SEVM

Hi,

I am using LMR14050SEVM and noticed that evaluation board is specked at 7V input minimum but IC is capable of up to 4V input. When I apply 7V input with a 4A load at 5V, output starts cycling from 0V to 5V. and Inductor becomes noisy.

Is IC not capable to handle 7V input?

Why IC and Eval board specked differently?

If not, what could be the reason for the eval board not working reliably at 7V input with 4A,5V output?

over 4 years ago

0 Marshall_Beck over 4 years ago

TI__Mastermind 30430 points

Output and Input voltage are correlated

The EVM Input and Output are dictated by stability generated by internal compensation and external devices including output cap and output inductor.

What ultimately dictates the IC low voltage is the device dropout performance.

0 Prabhat Kumar31 over 4 years ago in reply to Marshall_Beck

Prodigy 195 points

Does that mean LMR14050S will not operate reliably at 7V with 4A,5V output?

0 Andy Chen over 4 years ago in reply to Prabhat Kumar31

TI__Mastermind 27045 points

Hi,

output cycling maybe caused be below:

1. DC power supply has incorrect curremt limitation

2. actual input voltage on VIN pin drop below 5.2V if no change on EVM R1 and R2

3. Device enter thermal shutdown. the EVM can output 5V/4A with 7V input at room temperature.

0 Marshall_Beck over 4 years ago in reply to Prabhat Kumar31

TI__Mastermind 30430 points

Andy gave some valuable insights. Thanks Andy!

1. DC power supply has incorrect curremt limitation

At low VIN, DC input current is high for high IOUT

2. actual input voltage on VIN pin drop below 5.2V if no change on EVM R1 and R2

You could be hitting device UVLO.

3. Device enter thermal shutdown. the EVM can output 5V/4A with 7V input at room temperature.

You are making a decent amount of power. Maybe you are entering thermal shutdown due to layout that can be further optimized for thermals?

0 Prabhat Kumar31 over 4 years ago in reply to Marshall_Beck

Prodigy 195 points

Thanks Marshall.

It turns out that my power supply transient was causing the input to drop over 2V. I was hitting ICs UVLO.

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LMR14050SEVM: LMR14050SEVM output 5V, 4A at 7V input