INA296A: INA296A output has ringing on the rising and falling edges

zac zhang

Part Number: INA296A

Tool/software:

I am using INA296 for high current detection, but I have noticed ringing on both the rising and falling edges of the output. How can I solve this problem?

Channel1 is output voltage, ch2 is INA296 output, ch3 is current probe output.

below is schematic:

1 month ago

0 Javier Contreras4 1 month ago

TI__Mastermind 29770 points

Hello Zac,

This is due to the VCM transition, also known as AC CMRR. I am assuming that Ch1 = VCM, Ch2 = INA296_Vout, Ch3_ Expected Vout. The datasheet shows this image below. Also there is -100V in your schematic. The INA296 cannot be used with -100V VCM.

0 zac zhang 1 month ago in reply to Javier Contreras4

Prodigy 65 points

Thanks for your reply。 In my application, I short the -100V to ground, ch1 is VCM, which is about 50V and is within the range of INA296. It should be caused by other reasons. Can you give any other suggestions?

0 Javier Contreras4 30 days ago in reply to zac zhang

TI__Mastermind 29770 points

Zac,

I think this is the VCM transition. Look at the time differences from the two plots.

Regards,

Javier

0 Javier Contreras4 30 days ago in reply to Javier Contreras4

TI__Mastermind 29770 points

Zac,

Here is some response I had captured below. I placed a snubber on my GanFet used to create the VCM transient. You will notice there is no ringing on the VCM transient. I had to run some simulations to find my optimal snubber for my load and GanFet.

0 zac zhang 29 days ago in reply to Javier Contreras4

Prodigy 65 points

Hi Javier,

I understand what you said about VCM transition, but compared with the spec, the waveform measured is much larger, vpp is greater than 2V, how should I reduce this peak? thanks

0 Javier Contreras4 29 days ago in reply to zac zhang

TI__Mastermind 29770 points

Hello Zac,

Can you reduce the overshoot and ringing of the VCM by adding a snubber? The overshoot and ringing will be dependent on patristics and FET properties. I did something for my GANFET to get the results I displayed above. My schematic below I added many parasitics but the highlighted values is what I changed to get the lowest overshoot and ringing.

0 Javier Contreras4 28 days ago in reply to Javier Contreras4

TI__Mastermind 29770 points

Hello Zac,

I thought about it and there may be some other coupling from the VCM transient to the output.

Can you share your layout?

Regards,

Javier

0 zac zhang 16 days ago in reply to Javier Contreras4

Prodigy 65 points

Hi Javier, this is my layout, please check, thanks.(the C25 is DNI, U7 is DNI)

0 Louis L 16 days ago in reply to zac zhang

TI__Expert 4320 points

Zac,

Thank you for your patience.

Due to the U.S. holidays, Javier is currently out of the office and will reply when he returns on 1/6.

Louis

0 Javier Contreras4 2 days ago in reply to Louis L

TI__Mastermind 29770 points

Hello Zac,

Seem like there is no ground plane. The bypass cap is not placed optimal as well. As there seems to be a long path between the GND that is connected to the pin 2 (GND) and the GND pad of C24. I would also have GND plane under the Rshunt as a path for high frequency from your VCM transients.

Regards,

Javier

0 zac zhang 18 hours ago in reply to Javier Contreras4

Prodigy 65 points

Hi Javier, thanks for your reply. I will try to optimize my layout and test again.

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INA296A: INA296A output has ringing on the rising and falling edges