LM5140-Q1: control loop response testing

Andrew Lints

Part Number: LM5140-Q1

Hello,

I am using the lm5140 in a design with the default 3.3V and 5V outputs for Vo1 and Vo2. When the FB pins are tied to VDDA as shown in the reference schematic, What is the ideal ripple injection point for testing the control loop response?

I am using a sense resistor on the output, so my thought was to place a 20ohm resistor between on the sense line back to VOUT1 but this seems does not seem like the correct way to test. Is it required to use a resistor divider on the feedback pin and use a standard ripple injection resistor instead of tieing the pin to VDDA?

Thanks

over 7 years ago

0 Samuel Jaffe over 7 years ago

TI__Mastermind 25590 points

Andrew,

Good question. Let me ask the expert and get back to you on this.

-Sam

0 Samuel Jaffe over 7 years ago in reply to Samuel Jaffe

TI__Mastermind 25590 points

Andrew,

The expert was quick! There is no way to do the test you're trying to take in that configuration but there is a workaround. You can change the feedback resistors to achieve 3.3V and 5V, then add a resistor in series with the top FB resistor like you normally would.

Thanks,
-Sam

0 Andrew Lints over 7 years ago in reply to Samuel Jaffe

Prodigy 60 points

OK, Thank you for the quick response. I will update our schematic and test plans accordingly.

Thanks!

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LM5140-Q1: control loop response testing