LM25088-Q1: Function and calculation of Rramp in LM25088-Q1 Design

suraj jr

Part Number: LM25088-Q1
Other Parts Discussed in Thread: LM25088

I would like to know the function of Rramp resistor in the below configuration. Datasheet recommends Rramp ony for VOUT>5V but my VOUT is 5V. And also why a 1M ohm resistor is used.

Webench Design Link

Schematic:

over 3 years ago

0 Daniel Li14 over 3 years ago

TI__Mastermind 27490 points

Ramp is provide extra proper slope compensation for LM25088. I suggest you can leave it open if no issue when the circuit work. but if you found some unstable condition, you can try to assembly this resistor to see any improvement for stability.

Thanks

0 suraj jr over 3 years ago in reply to Daniel Li14

Prodigy 10 points

Hi,

Thank you. But why is a 1M ohm resistor and why is it pulled up to Vvcc and not Vin.? Plus how does the Rramp help in slope compensation.

0 Daniel Li14 over 3 years ago in reply to suraj jr

TI__Mastermind 27490 points

1M ohm can privde around 7.8uA extra slope compensatin(internal is 25uA) connect to Vin will make the sloep compensation current too large.

Thanks

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LM25088-Q1: Function and calculation of Rramp in LM25088-Q1 Design