LM63635-Q1: Schematic issues

Ray Tong

Part Number: LM63635-Q1

Hello! We are currently using the LM63635DQDRRRQ1 primary power supply; The specification book mentions this filtering circuit;

Is R 0.51 Ω in this box a resistor that must be used with this resistance value? Do you have any suggestions for the resistance value of this resistor? Can it be removed?

over 2 years ago

0 Gui He over 2 years ago

TI__Mastermind 27936 points

Let me check about this and get back later.

0 Ray Tong over 2 years ago in reply to Gui He

TI__Intellectual 1330 points

hi Gui

May I ask if there are any results

0 Shipeng Cheng over 2 years ago in reply to Ray Tong

TI__Mastermind 18020 points

Hi Ray,

Here are the impedance with and without the resistor. So With the resistor, the gain peak can be damping. Then the noise near 20kHz will not be amplified. This is sometimes useful for EMI performance.

BR,

Shipeng

0 Gui He over 2 years ago in reply to Ray Tong

TI__Mastermind 27936 points

Hi Ray

Sorry for late reply, and thank you shipeng for covering this.

The resistance is needed in the input filter network ,otherwise, the attenuation is not enough at the resonant peak, and there might be instability issue caused by the filter inductor and the Cin of the converter.

The 47uF cap has ESR and provides the damping. Usually we don't need the 0.51Ohm. The 0.51Ohm should provide similar damping impact. Customer can have it on board and NC if they have concerns.

Thanks and best regards.