TPS2492: MOSFET Selection - Secondary Breakdown

LIN

Part Number: TPS2492

Datasheet Page 26

M1 Selection

Use of a power FET in the linear region places large, long term stresses on the distributed junction. FETs whose safe operating area (SOA) curves display multiple slopes on the same line (e.g. a line whose time parameter is a constant) in the region of high voltage and low current generally are susceptible to secondary breakdown and are not strong candidates for this application. An example of a good choice is found in the Typical Application Circuit where the line at 10 ms shows no breaks in slope. The best device for the application is not always the lowest RDSON device.

I thought RDS(ON) and thermal resistance are most important so less cooling measures are required for the MOSFET.

I don't really understand why SOA with multiple slopes are not strong candidates. Any advice?

Is secondary breakdown same as avalanche? I thought all power MOSFETs are subjected to avalanche, right?

Thanks.

over 5 years ago

0 Rakesh over 5 years ago

TI__Guru* 95671 points

Hi Aibing,

The FET will be subjected to severe power stress during system turn ON. Please go through APP note www.ti.com/.../slva673a.pdf which covers most of the details.

Best Regards,
Rakesh

0 LIN over 5 years ago in reply to Rakesh

Intellectual 410 points

Hi Rakesh,

Thanks.

1. The Application Note (slva673a) mentions,
To ensure proper operation, most controllers will have a minimum recommended VSNS,PL,MIN that should be adhered to.

What is VSNS,PL,MIN for TPS2492?

2. The Application Note (slva673a) also recommends the dv/dt control circuit. With the dv/dt control circuit, any adverse effects on gate control for hot-swap, power-limiting and current limiting?

0 Rakesh over 5 years ago in reply to LIN

TI__Guru* 95671 points

Hi Aibing,

1A> The design calculator has information of VSNS,PL,MIN for TPS2492. Refer "TPS249x_8x Design Calculator Rev_B (Rev. I)" available at

2A> dv/dt control circuit will be active during startup and in normal operation, the current limiting function remains same.

for higher value of external cap, use below configuration

Best Regards,

Rakesh

0 LIN over 5 years ago in reply to Rakesh

Intellectual 410 points

Hi Rakesh,

Thanks.

I did not manage to find VSNS,PL,MIN for TPS2492 in the excel file. What is the value there and is this shown in any document?

0 Rakesh over 5 years ago in reply to LIN

TI__Guru* 95671 points

Hi Aibing,

I see the values in row 62.

Best Regards,

Rakesh

0 LIN over 5 years ago in reply to Rakesh

Intellectual 410 points

Hi Rakesh,

Thanks. The TPS249x_8x_Design_Calculator_REV_B.xlsx shows blank on Column E and F, as attached screen capture. If click on the cell, the content shows on top input box, the cell is still blank.

How to resolve this?

0 Rakesh over 5 years ago in reply to LIN

TI__Guru* 95671 points

Hi Aibing,

Choose 'Yes' in rows 22 & 23 to enable the calculator

Regards,
Rakesh

0 LIN over 5 years ago in reply to Rakesh

Intellectual 410 points

Hi Rakesh,

Thanks. It works.

Power management

Power management forum

TPS2492: MOSFET Selection - Secondary Breakdown