TPS40211 EVM - Q2 mosfet Blows up.

Ashirbad Panda

Other Parts Discussed in Thread: TPS40211

Hi,

Setup : Input 8V to 18V

Output : 20V - 35V, 700mA (as in the EVM)

While using the evaluation board ,when the Input voltage remains constant at around 4.2V then MOSFET Q2(Si7854DG ) gives a beeping sound and after around 5 seconds it blows up. This situation is when the voltage cut off is set at 4.5V.

Next when we have increased the input voltage cutoff to 10V, then at around constant input voltage of 9.3V the MOSFET again gives a beeping sound and blows up.

What is the reason for this failure??

over 14 years ago

0 Richard Garvey over 14 years ago

TI__Expert 4375 points

Ashirbad,

Not sure what exactly you are doing with the EVM. What load do you have connected to the output? Is the EVM set up per the diagram of figure 2 in the user guide, http://focus.ti.com/lit/ug/sluu351/sluu351.pdf ? Have you made any modifications to the EVM, you mention Si7854 but the EVM uses Si7850? Prior to failure what is the waveform on pin 8 of the IC (TPS40211) doing?

Thanks,

Richard.

0 Ashirbad Panda over 14 years ago in reply to Richard Garvey

Prodigy 20 points

Dear Sir,

First of all I am sorry ,that I have mentioned the wrong part Si7854, it is Si7850 that blows up.

I had connected 2 LED strings with 6 LEDs per string.

What exactly happens is when I lower down the voltage slowly then at around 4.2V the MOSFET starts beeping and then blows up.

Thanks

Ashirbad

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TPS40211 EVM - Q2 mosfet Blows up.