RC filter design for current sense input of LM5030

Thread Starter

Arbitrage

Joined May 3, 2021
17
Hi,
I wanted to design a RC filter connected between the current sense resistor and current sense pin for eliminating noises, I have gone through many articles and datasheet of lm5030 but didn't find how to select the values of R and C, I have attached a example here with another ic,here r19 is current sense resistor ,r22 and c13 form the rc filter,also attaching datasheet of ic
1628255045523.png
 

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Ian0

Joined Aug 7, 2020
3,463
Usually, I would expect that you wanted to eliminate the spike which happens when the MOSFET turns on.
If so, measure the time duration of the spike, and make the time constant R22*C13 two or three times the length of the spike.
Don't filter it too well, as the LM5030 needs to see the slope of the voltage on the CS input!
 

ericgibbs

Joined Jan 29, 2010
13,825
hi A,
Welcome to AAC.
Is this circuit part of a PCB layout, if so a photo shot of the PCB showing the copper tracking of the GND and the two Common/Gnd symbol points, would help.

What noise levels do you measure on a scope.?

E
 

Thread Starter

Arbitrage

Joined May 3, 2021
17
hi A,
Welcome to AAC.
Is this circuit part of a PCB layout, if so a photo shot of the PCB showing the copper tracking of the GND and the two Common/Gnd symbol points, would help.

What noise levels do you measure on a scope.?

E
Thanks for your reply, actually I don't have the pcb ,just the simulation file ,but the issue is sorted now,thanks
 

Thread Starter

Arbitrage

Joined May 3, 2021
17
Usually, I would expect that you wanted to eliminate the spike which happens when the MOSFET turns on.
If so, measure the time duration of the spike, and make the time constant R22*C13 two or three times the length of the spike.
Don't filter it too well, as the LM5030 needs to see the slope of the voltage on the CS input!
Thanks it helped
 
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