TPS40090: Accuracy impact for CS inputs beyond 100mV

Matt Calvo

Part Number: TPS40090

Tool/software:

Hey Multiphase Buck Team,

I have a customer evaluating the TPS40090 for a new project and we were hoping you could help to provide feedback on the inquiry below!

It is our understanding that if the CS inputs go beyond 100mv then then there is a degradation in accuracy. Our interpretation of this is that if the CS signals go beyond 100mV then the there is non-linearity of the gain value. Can TI provide a curve that shows the “g” gain over the range of CS voltages from 0V to 200mV? If it turns out that it is not the current amplifier gain that causes the inaccuracies, then we would still like to understand the possible variance out to 200mV.

-Matt

11 months ago

0 Mahmoud Harmouch 11 months ago

TI__Mastermind 28340 points

Hello,

I'm looking at and will post the answer in 2 days.

Regards

0 Matt Calvo 11 months ago in reply to Mahmoud Harmouch

TI__Genius 14755 points

Thanks for the update Mahmoud; looking forward to your feedback!

-Matt

0 Mahmoud Harmouch 11 months ago in reply to Matt Calvo

TI__Mastermind 28340 points

Hello, I tried to modify the EVM and measure the gain beyond 100mV but the documentation is not clear. I'm trying to find to original file and hope it still in the system. Sorry for the delay but it will take longer than expected. I will try with our test team if they can test it on ATE.

Regards

0 Mahmoud Harmouch 11 months ago in reply to Mahmoud Harmouch

TI__Mastermind 28340 points

Hello,

I checked the ATE test data and the gain is measured at 200mV. It is 4.88V/V.

Regards

0 Matt Calvo 11 months ago in reply to Mahmoud Harmouch

TI__Genius 14755 points

Thanks for the info Mahmoud!

I'll pass this along to my customer and will have them comment back on this thread directly with any follow-up questions they may have.

-Matt

0 Mahmoud Harmouch 11 months ago in reply to Matt Calvo

TI__Mastermind 28340 points

Hi Matt, I measured the current shutdown threshold and is not matching the datasheet formula. In my experience:

- current limit per phase 38A

- 4 phases system

- shutdown threshold voltage is 114mV

- Inductor DRC = 1.7 mOhms

The calculation should give 174.5mV but in practice it is only 114mV.

It seems the same thing happens in customer board.

Regards

0 Mahmoud Harmouch 11 months ago in reply to Mahmoud Harmouch

TI__Mastermind 28340 points

Hello,

please ignore my last post. It is for same part but different subject.

Regards

Power management

Power management forum

TPS40090: Accuracy impact for CS inputs beyond 100mV