LM5145DESIGN-CALC: Audio forum

user6150978

Prodigy 40 points

Part Number: LM5145DESIGN-CALC
Other Parts Discussed in Thread: LM5145

A new project needs to output 15v10a for 24V power input. LM5145 is considered.

The design is shown in the figure below.

Q1 is burnt out when it is designed and used.

After Q1, Q2 and L1 are removed, the oscilloscope tests that HO is 6V and LO has 540K pulse signal.

Please help me to analyze. What's the problem?

Thank you！！！

over 5 years ago

0 Daniel Li14 over 5 years ago

TI__Mastermind 27470 points

Hi :

there is seveal place not good in the schematic:

1 CSD18504 Rdson is 5.3mhom , with 1k Rlimit, the over current will over 40A which will make the fet burnout

2. with 44uF output cap and 2.2uH output choke, the LC resonant point is at 5.7Khz, but you compensation network double zero is at 1.3Khz and 53Khz, which can't compensat the LC double pole . the whole system will be unstable. which easily make the fet burn out either.

3. the divide resistor value shows the output is 8.5V instead of the 15V output.

so you can follow the cacualtion tools , and make the compensation and current limt is fit for your system requirment. it may become better.

Thanks

Daniel Li

0 user6150978 over 5 years ago in reply to Daniel Li14

Prodigy 40 points

Thanks for your reply。

The parameters of the circuit are generated by using webnch. Can we see the parameters of the accessories?

Please point out if there is any problem.

LM5145 WEBNCH DESIGN.pdf

0 user6150978 over 5 years ago in reply to user6150978

Prodigy 40 points

The adjustment parameters are R4=18K，C5=10uF，C6=10uF

0 Daniel Li14 over 5 years ago in reply to user6150978

TI__Mastermind 27470 points

I wil check the webench simualtion internally, I think the value is not right esepcailly output cap.

I recommend you can use below caculator for schematic.

https://www.ti.com/lit/zip/snvc206

Power management

Power management forum

LM5145DESIGN-CALC: Audio forum