LM5140-Q1: LM5140-Q1 output inductor hot

dengshan yang

Prodigy 155 points

Part Number: LM5140-Q1
Other Parts Discussed in Thread: LM5143-Q1

hi,

I designed a power solution---24V input, 12V/20A and 5V/5A dual output, the design is below, about 12V output,

1.change current sense resistor from 0.004 to 0.002

2. change inductor from 10uh to 0.68uh with higher Isat,

3. set up switch frequency 440KHz

but I found the current was very hot without load when power up.

Jerry

over 2 years ago

0 dengshan yang over 2 years ago

Prodigy 155 points

sorry, it shoud the inductor was very hot without load when power up. I typo it.

0 Timothy Hegarty over 2 years ago in reply to dengshan yang

TI__Mastermind 49207 points

Hi Jerry,

Please send a completed LM5140-Q1 quickstart calculator for this design. You will need to increase the inductance if Fsw = 440kHz.

Btw, the 47pF cap should go from COMP to GND (not in parallel with Ccomp).

Regards,

Tim

0 dengshan yang over 2 years ago in reply to Timothy Hegarty

Prodigy 155 points

hi Tim,

sorry, I can't attached a completed LM5140-Q1 quickstart calculator for this design, due to no path to upload.

0 dengshan yang over 2 years ago in reply to Timothy Hegarty

Prodigy 155 points

Timothy Hegarty said:
Hi Jerry,

Please send a completed LM5140-Q1 quickstart calculator for this design. You will need to increase the inductance if Fsw = 440kHz.

Btw, the 47pF cap should go from COMP to GND (not in parallel with Ccomp).

Regards,

Tim

0 Timothy Hegarty over 2 years ago in reply to dengshan yang

TI__Mastermind 49207 points

Hi Jerry,

Please send the file and update the shunt and inductor values as needed. The ripple current should be ~30-50%.

25A per phase is quite high, so the design needs to be optimized for thermals. Please use 40V FETs.Recommendation to the change to the LM5143-Q1 (very similar pinout to the LM5140-Q1, but it has more functionality - in particular resistor-programmable Fsw).

Regards,

Tim

Power management

Power management forum

LM5140-Q1: LM5140-Q1 output inductor hot