TPS40322: VFB

Julian Chen

Expert 2550 points

Part Number: TPS40322

Hi E2E,

We use TPS40322 2-Phase solution and find VFB will from 0.6V rising to 0.606V when heavy load.

We also use fan to cool down the IC , but no any improve.

Did you have any idea to fix this issue?

over 4 years ago

0 Qian Chen over 4 years ago

TI__Mastermind 24075 points

Hi Julian,

Did you measure the voltage between FB pin (pin 4) and AGND pin (pin 6) ?

Also, can you measure the voltage between pin 11 and pin 10 at no load and heavy load condition?

Thanks

Qian

0 Julian Chen over 4 years ago in reply to Qian Chen

Expert 2550 points

Hi Qian,

Feedback resistor: RGND=9.31K ; Rtop=42.2k

No load :
VFB to AGND (Pin 4 to Pin 6) = 0.6V
Remote sense (Pin 11 to pin 10) = 3.327V

Heavy load (33A):

VFB to AGND (Pin 4 to Pin 6) = 0.606V
Remote sense (Pin 11 to pin 10) = 3.364V

We also change the Feedback resistor: RGND=2.2K ; Rtop=10k to avoid noise, but the no any improve.

0 Qian Chen over 4 years ago in reply to Julian Chen

TI__Mastermind 24075 points

Hi Julian,

In datasheet spec table (page 7), the FB variation is 0.594V to 0.606V when Tj is between -40c and 125c.
Is the part hot with 33A load?

Another question, how many boards do you have?
Can you test a few more boards to see if the result is the same?

Thanks
Qian

0 Qian Chen over 4 years ago in reply to Qian Chen

TI__Mastermind 24075 points

HI Julian,

We don't hear from you for some time.

I'm going to close this case. Please let me know if you need further support.

Thanks

Qian

0 Julian Chen over 4 years ago in reply to Qian Chen

Expert 2550 points

Hi Qian,

Sorry to reply late.

We observe the waveform then find the FB had switch noise.
I will assist customer to modify layout to improve this issue.

Thanks a lot.

Power management

Power management forum

TPS40322: VFB