DRV8818: SOA of the output FET

NAOKI AOYAMA

Guru 11215 points

Part Number: DRV8818

Hello,

Our customer use the DRV8818.

The customer connect a capacitor between xOUTx and GND to reduce EMI noise.

The value of a capacitor is 6800pF or more.

I suggested the customer check the current and not to exceed the OCP level and OCP

glitch time.

So, the customer have a one more question.

How about the SOA of the output FET?

I think the analog limit circuit operate and reduce a current under SOA region.

Is it correct?

Best Regards,

Naoki Aoyama

over 8 years ago

0 Rick Duncan over 8 years ago

TI__Guru** 114905 points

Hi Aoyama-san,

You are correct. There is an analog circuit to limit the current.

0 NAOKI AOYAMA over 8 years ago in reply to Rick Duncan

Guru 11215 points

Hi Rick-san,

Thank you for your reply.

Thanks,
Naoki Aoyama

0 NAOKI AOYAMA over 8 years ago in reply to Rick Duncan

Guru 11215 points

Hello Rick-san,

May I ask one more question?
Perhaps, the customer will connect larger capacitor in someday.
Do you have any data or any experience using the DRV8818 with large capacitor?
or
Do you have any idea the value of a capacitor that should not to connect?

Regards,
Naoki Aoyama

0 Rick Duncan over 8 years ago in reply to NAOKI AOYAMA

TI__Guru** 114905 points

Hi Aoyama-san,

Please see the application report www.ti.com/.../slva670a.pdf

Equation 1 can be used as an approximation. Capacitor tolerances should be considered.

0 NAOKI AOYAMA over 8 years ago in reply to Rick Duncan

Guru 11215 points

Hi Rick-san,

Thank you for your advice.
I will calculate an inrush current.

Thanks,
Naoki Aoyama

0 NAOKI AOYAMA over 8 years ago in reply to Rick Duncan

Guru 11215 points

Hello Rick-san,

Could you tell me one more thing?

I have a question about analog limit circuit on the application note 'slva505'.

Figure 2 shows a oscilloscope capture of a short circuit event.

A current flow as 15A momentarily.

Is it a problem for SOA?

DRV8818_SOA.pdf

Best Regards,

Naoki Aoyama

0 Rick Duncan over 8 years ago in reply to NAOKI AOYAMA

TI__Guru** 114905 points

Hi Aoyama-san,

This is not a problem for SOA.

0 NAOKI AOYAMA over 8 years ago in reply to Rick Duncan

Guru 11215 points

Hi Rick-san,

Thank you for your reply.
I will feedback the customer this information.

Thanks,
Naoki Aoyama

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DRV8818: SOA of the output FET