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Beep Capacitor in driver A3941

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kolines

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Hello All,

I have been listening to an annoying beep on the circuit board that I mount and now I decided to look from where it came from as it spread all over the circuit board and it was difficult to know if it came from the coils or other capacitors, what it was.

This is the capacitor that goes on pins 7 and 8 (Vreg) of the driver A3941, this ceramic capacitor of 22uF / 25V (digi-key 445-9112-1-ND) emits a beep. This capacitor I do not know how to calculate it.
Also as recommended Allegro is close to the driver's pins.

The maximum voltage according to the datasheet is 13.75V in Vreg when measuring I get 13.5V.

I would like to know the reason for that sound beep or if I have to switch to another capacitor,

Thank you.
 

Hi,

--> read about ceramic capacitors and their piezoelectric behaviour.

This is a known and frequently discussed topic.

Klaus
 

Hello,

Thanks for the reply, I'll check it later.
But you can not avoid or eliminate the noise as it is quite annoying and at the same time I change the PWM, the sound is more annoying.
I do not know if I can put an electrolytic capacitor in A3941

THX.
 

Hi,

I do not know if I can put an electrolytic capacitor in A3941
Click to expand...
Similar recommendation as above:
--> read A3941 datasheet. It will tell you what capacitors you may use and what you should care about.

Klaus
 

Hi,

My calculations are:

CBoot= (Qg*20)/Vboot = (236nC*20)/13V=390nF
390nF*2=780nF = 1uF (Parallel Mosfets by double capacitance)

CVReg = (CBoot * 20) = 1uF * 20 = 20uF / 25V

Datasheet Max VReg= 13,75V

I do not know if you can put an electrolytic capacitor or polyester.

PCB photo, capacitor closed A3941 driver.


A3941 PCB CReg 2.jpg

THX.
 

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