DRV8818: Cap value on VCP, CP1 and CP2

Takashi Onawa

Part Number: DRV8818

Hi Team,

One quick question.

Regarding the Cap for the CP, datasheet says as below. I understand TI recommends 0.22uF rated value but effective value is varied depending DC biasing, right? So my question is "how much effective value(at what voltage) is need for safety operation of DRV8818?"
Recently, ceramic cap is getting smaller due to suppliers strategy and effective value is also getting smaller at same voltage level due to the size down.

A low-ESR ceramic capacitor must be placed in between the CP1 and CP2 pins. TI recommends a value of 0.22-μF rated for VM. Place this component as close to the pins as possible. A low-ESR ceramic capacitor must be placed in between the VM and VCP pins. TI recommends a value of 0.22-μF rated for 16 V. Place this component as close to the pins as possible.

Regards,

Takashi Onawa

over 3 years ago

0 Ryan Kehr over 3 years ago

TI__Guru 54645 points

Onawa-san,

Please see the response in this post.

0 Takashi Onawa over 3 years ago in reply to Ryan Kehr

TI__Genius 13200 points

Hi Kehr-san,

Thanks for your prompt response on this.

I almost understood TI recommendation and its behaviors but let me check the typ voltage range between VCP and VGD?

My customer plan to put some additional cap to secure -50% of 0.22uF as effective cap value but it might go beyond +50% depending on the voltage range.

Regards,

Takashi Onawa

0 Ryan Kehr over 3 years ago in reply to Takashi Onawa

TI__Guru 54645 points

Onawa-san,

Voltage on VCP pin is ~11V above VM, so delta voltage across cap is ~11V. That is why we recommend a 16V capacitor.

Voltage across CP1/CP2 cap is approximately VM - one diode drop. That is why we recommend the same voltage rating on this cap as you would use for the VM decoupling capacitors.

0 Takashi Onawa over 3 years ago in reply to Ryan Kehr

TI__Genius 13200 points

Hi Kehr-san,

Thanks, I understood.

Sorry, one more confirmation about Cap for VGD.

Can we regards as the DC voltage is also 11V delta for VGD-GND?

Regards,

Takahshi Onawa

0 Ryan Kehr over 3 years ago in reply to Takashi Onawa

TI__Guru 54645 points

Onawa-san,

VGD voltage is slightly lower at ~8V, but we still recommend a 16V capacitor as a 10V capacitor would not leave enough margin.

0 Takashi Onawa over 3 years ago in reply to Ryan Kehr

TI__Genius 13200 points

HI Kehr-san,

Thanks for your prompt response on this .

I understood .

Regards,

Takashi Onawa

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DRV8818: Cap value on VCP, CP1 and CP2