TPS61181A: TPS61181A - Short-Circuit Protection

Hi Jose,

The fault pin of this IC can be used to control an isolation FET on power line. When short-circuit, the output voltage will ramp down and when Vo is 1.7V lower than Vin, the IC will shut down the isolation FET to cut off the path that Vin to Vo, and the IC will shut down as well.

BR

Patrick

Hi Patrick,

If I've understood the manual correctly, and what you're saying, then nothing should happen when there's a short circuit.

Here's the test we did on the TPS61181A-EVM board:

We connected a series of LEDs to each of the 6 IFB inputs, and they all lit up as expected. When we simulated a short circuit in one series of LEDs, they all went off, and never came back on again. We did power-off / power-on and nothing happened !

Please note that the short-circuit we simulated was not permanent, but just the simple touch between two wires, which didn't even take a second.

After some measurements, we found that the TPS61181A was damaged and had to be replaced.

In addition, the Si2307 MOSFET was also damaged by a short-circuit between Drain and Source, so it also had to be replaced.

Only after the replacement did everything work normally again.

We therefore don't know how the short-circuit protection works if an IFB pin is short-circuited by Vo - in this case the protection was to burn the TPS61181A and the Mosfet.

Thank you in advance for your comments on this matter, as what has happened makes us concerned about the use of the TPS61181A in this project.

regards

Jose

Hi Jose,

Could you please send me your schematic for double check?

BR

Patrick

Hello Patrick ,

As I mentioned earlier, we used the TI demo board with part-number TPS61181A-EVM, so the documentation is available online.

regards

Jose

Hi Jose,

Noted, and could you please share more test setup conditions with me? What are the Vin, ILED and VLED? And may I know how did you simulate the short-circuit (which two wires were connected together?) Thanks

BR

Patrick

Hi Patrick,

Please find below the test conditions

Vin = 13.30V

I_led = 5.72 mA (R = 215K)

3 led strips with 8 white leds each, connected to IFB1, IFB2, IFB3

Shunt made on IFB4 with Vo with 2 wires
only one wire touched the other lightly, without the shunt being permanent.

regards,
Jose

Hi Jose,

Ok, please allow me some time to check, thanks

BR

Patrick

Hi Jose,

The IFB pins have a maximum 20V voltage tolerance, so if you directly connect IFB to Vo (8 LEDs will be over 20V), there might be potential risk to damage the IC. I think the short-circuit protection is mainly for Vo short to GND but not short to IFB.

BR

Patrick

Hi Patrick,

I'm surprised, as I never noticed this when reading the datasheet.

Is what you mention indicated in the datasheet?

Can you please indicate where and how this is described in the manual?

regards

Jose

Hi Jose,

You can refer to datasheet "7.1 Absolute Maximum Ratings" for the max voltage on IFB.

BR

Patrick

Hi Patrick,

Thanks for the reply, but that wasn't my question.

The question is how is it indicated in the manual that the short-circuit protection is between Vo and Gnd as you said, and not between Vo and an IFB pin?

regards,

Jose

Hi Jose,

Because this is an old device, our new device usually treats Vo short to IFB as a special condition of LED short. And Vo short to GND as short-circuit. It is not listed in this IC datasheet.

BR

Patrick

Hi Patrick

Even though it's an old component, TI should detail this fact in the datasheet to avoid drawing the wrong conclusions.

Is there a new component, compatible with the current one, that already has the protection between Vo and IFB pins?

regards,

Jose

Hi Jose,

Thanks for the suggestion. And as I mentioned, Vo short to IFB can be treated as a special condition of LED short, so it has been protected by LED short protection. But if the Vo is larger than the maximum V_IFB, there will be potential risk to damage the IC if you short Vo to IFB directly.

BR

Patrick

HI Patrick,

Thank you for your reply, but you haven't answered the second question.
Is there a component compatible with the TSP61181A that has effective protection for a shunt between Vo and the IFB pin, regardless of the value of the Vo voltage?

regards

Jose

Hi Jose,

So will you only consider pin-to-pin solutions? From my side, TPS92380 seems more suitable for your application.

BR

Patrick