Questions for LM5576

Randy Chen

Intellectual 2295 points

Other Parts Discussed in Thread: LM5576

Hi,

Two questions about LM5576 and need your help.

There is no R_ramp(R5) in the LM5576EVM reference design but shown in the calculation tool. Should R_ramp be installed in the design?
Customer is preferring inductor with 22uH/current rating 4A. Calculation recommend 33uH/5.1A base on F_sw 300KHz. Any concern if raise the F_sw to 450KHz for fitting inductor 22uH?

over 9 years ago

0 Akshay Mehta over 9 years ago

TI__Genius 15810 points

Please attach your schematic with the input and output requirements as well. Thanks!

0 Randy Chen over 9 years ago in reply to Akshay Mehta

TI__Intellectual 2295 points

 Input Voltage : 19V ~ 50V
 Output Voltage : 12V
 Rated current : 3A

0 Akshay Mehta over 9 years ago in reply to Randy Chen

TI__Genius 15810 points

Hello,
Rramp is needed for slope compensation. The internal ramp added is not enough for higher VOUTs and therefore for higher VOUT, you have to add a resistor. I would suggest them to do a WEBENCH design and optimize for higher frequency. At 500kHz they can use a 22uH inductor.
Regards,
Akshay

Power management

Power management forum

Questions for LM5576