LM5066: Driving issue for 6pcs MOSFETs

Tseng Albert

Prodigy 50 points

Part Number: LM5066

Hi,

I have a drive issue about using LM5066 to drive 6pcs MOSFETs parallel.

The channel of waveform shown as below are Input voltage(CH1), output voltage(CH2) and Vgs(CH4)

If the output Load is 0A, the Vgs signal of Mosfet rise smoothly.

When output load is a small load, like 2~5A, the Vgs signal reach mosfet threshold voltage for a while, then GS, DS of Mosfet are burns.

But if I use 1psc mosfet and add one capacitor across gs terminal to simulate same Ciss of 6pcs mosfet.

Mosfet wolud not burn when output drawing the power.

How to check if I can support 6 or more MOS parallel?

Thanks.

over 5 years ago

0 Kuan Wei Chen (Kevin Chen) over 5 years ago

TI__Genius 9710 points

Dear Team,

The customer is using this MOSFET:
FDMS2D5N08C-D
BR
Kevin

0 Kuan Wei Chen (Kevin Chen) over 5 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Genius 9710 points

Dear Team,

The schematic:

0 Rakesh over 5 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Guru** 103506 points

Hi,

I will check and get back to you in the next week.

Best Regards,
Rakesh

0 Rakesh over 5 years ago in reply to Rakesh

TI__Guru** 103506 points

Hi Tseng Albert,

Welcome to E2E!

What is the purpose of RA289 ? Is there any additional capacitance apart from 100uF shown in the schematic?
Can you please fill up the design calculator and send me for review. It is available at www.ti.com/.../toolssoftware

Best Regards,
Rakesh

0 Tseng Albert over 5 years ago in reply to Rakesh

Prodigy 50 points

Dear Rakesh

I have two way to drive MOS, one is LM5066, another is a analog circuit.

RA289 is for my analog circuit to insure VGS=0V when driver not working.

Output capacitance is only 100uF.

The design calculator as attachment.

LM5066I_Albert.xlsx

Thanks.

0 Rakesh over 5 years ago in reply to Tseng Albert

TI__Guru** 103506 points

Hi Tseng Albert,

Can you check the startup with out RA289. The device LM5066 has only 20uA charging current, so 10kOhm between GATE to Source may not allow GATE voltage to rise.
Can you also share the complete schematic, meanwhile I will review the design sheet.

Best Regards,
Rakesh

0 Rakesh over 5 years ago in reply to Rakesh

TI__Guru** 103506 points

Hi Tseng Albert,

Did you get chance to test without RA289?

The design calculator shows poor SOA for the desing, please consider stronger FET something like PSMN4R8-100BSE

Best Regards,
Rakesh

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LM5066: Driving issue for 6pcs MOSFETs