LM5175

Laif Hanno

Other Parts Discussed in Thread: LM5175

I develop a DCDC-converter (LM5175)

V_in:9V-18V

V_out:12V

I_out:20A

f_sw: 300kHz

I used the webench to design the PCB.

After start-up the DCDC-converter open-circuited  PIN between SW1-HDRV1 is low resistance and the LM5175 is destroyed.

I used several LM5175 and locate the same problem (PIN SW1-HDRV1 is low resistance).

I used input- and output filter and RC-Snubber (parallel LOW-Buck MOSFET and High Boost MOSFET).

So, I use support to locate the cause of the defect, please.

Kind regards

over 7 years ago

0 Christopher Dean over 7 years ago

TI__Intellectual 1745 points

Hi Laif,

I will contact an engineer familiar with this part. In the mean time, can you provide a schematic of the design?

0 Laif Hanno over 7 years ago in reply to Christopher Dean

Prodigy 60 points

Hi Christopher,

thank you very much.
Can I send you an EAGLE-file or do you need the schematic as a PDF?

0 Christopher Dean over 7 years ago in reply to Laif Hanno

TI__Intellectual 1745 points

PDF should be fine.

0 Laif Hanno over 7 years ago in reply to Christopher Dean

Prodigy 60 points

For Power inductance and MOSFETs I use following components:

Power inductance: WE 7443556082 (820nH)
Buck-MOSFETs: BSC010N04LS
Boost MOSFETs: BSC009NE2LS

Hope it is understandable.

0 Laif Hanno over 7 years ago in reply to Laif Hanno

Prodigy 60 points

Sorry, I have a Problem to send you the Images.
Can I send the PDF directly to you?

0 Christopher Dean over 7 years ago in reply to Laif Hanno

TI__Intellectual 1745 points

LM5175-20A.tsc

LM5175Schematic.pdf

here are the schematic as pdf and TI Tina schematic file from webench. uploaded to preserve in conversation.

0 Vijay86929 over 7 years ago in reply to Christopher Dean

TI__Genius 11490 points

Hi Laif,

I think 20A is a lot of current for a single phase design.
As for the BOOT-SW failure, it can be caused by ringing on the switch node and the consequent overcharging of boot capacitor. I suggest using a 8.2V small zener between BOOT1-SW1 and between BOOT2-SW2 to clamp the CBOOT1 and CBOOT2 voltages below their abs max.

The following app note explains how too much ringing can cause issue.
www.edn.com/.../Controlling-switch-node-ringing-in-DC-DC-converters
Please let me know if this does not help.
Thanks and regards,
Vijay

0 Laif Hanno over 7 years ago in reply to Vijay86929

Prodigy 60 points

Hi Vijay,

thanks for you answer. I'll try it and give you an feedback.

Thanks and kind regards
Laif

0 Laif Hanno over 7 years ago in reply to Laif Hanno

Prodigy 60 points

Hi Vijay,

the 8.2V small zener between BOOT1-SW1 and between BOOT2-SW2 was the solution to this problem.
Thanks very much.
But now, I have a a Problem with the Output-Voltage. In Boost Mode, the voltage is unstable at an Output-Current about 3A.
The other modes are stable.

Thanks and kind regards
Laif

0 Vijay86929 over 7 years ago in reply to Laif Hanno

TI__Genius 11490 points

Hi Laif,

The schematic file you have uploaded is not clear enough to read values. But I suggest you check your compensation and component values using LM5175 quick-start tool (excel based) on LM5175 webpage (tools and software).

Hope that helps.

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LM5175