DRV8243H-Q1EVM: Output voltage slightly drops periodically

Masaru Oinaga

Intellectual 2340 points

Part Number: DRV8243H-Q1EVM
Other Parts Discussed in Thread: DRV8243-Q1, , LM74610-Q1

Hello, Team,

We have 2 questions related to DRV8243-Q1 and its EVM.

Customer found out that there is a periodical voltage drop when using DRV8243H-Q1EVM:

Frequency is 2.5kHz and the device is in a full-bridge operation. VM = 18V supplied from a stable power supply.
Every 1.284 sec, there is a slight voltage drop as seen in the above figure.

What would be the reason? Can we fix this?
When VM pin = 0V but nFAULT pin pulled up with 10kOhm, is it ok with this condition which current flows?

Best Regards,
Masaru

over 1 year ago

0 Ryan Kehr over 1 year ago

TI__Guru 54645 points

Hello,

1) Can you zoom in on the voltage drop points? How much drop is measured? What is the load in this case? It would be good to also try another supply. I know you said it is stable, but this is strange.

2) This is no issue. nFAULT is an open-drain output. With VM = 0V, FET will not be turned on.

Regards,

Ryan

0 Masaru Oinaga over 1 year ago in reply to Ryan Kehr

TI__Intellectual 2340 points

Hello, Ryan,

Thank you for the reply

Let me attach the original excel sheet:

モータドライバ質問_20221117.xlsx

Sheet which says "問い合わせ事項" has the graph. From what it seems, the drop is less than or equal to 1V.
Let me also ask the customer to see if they can try it with another power supply.

Best Regards,
Masaru

0 Ryan Kehr over 1 year ago in reply to Masaru Oinaga

TI__Guru 54645 points

Hello again,

I don't see a zoom in imagine. Trying to determine if something is changing on the control side that would cause this.

Regards,

Ryan

+1 Masaru Oinaga over 1 year ago in reply to Ryan Kehr

TI__Intellectual 2340 points

Hello, Ryan,

We found out that it is caused by the ideal diode controller LM74610-Q1 installed prior to the PI filter of the EVM.
This IC does not have a 100% duty cycle and thus drops periodically because of its body diode (VF).

Best Regards,
Masaru

0 Ryan Kehr over 1 year ago in reply to Masaru Oinaga

TI__Guru 54645 points

Hello!

Ah, this makes sense. I now remember seeing this on one of our EVMs. Thank you for the follow-up!!

Regards,

Ryan

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DRV8243H-Q1EVM: Output voltage slightly drops periodically