UC3906 burned

Stachiotti Fernando

Other Parts Discussed in Thread: UC3906, BQ24105, BQ24450

I made 5 prototypes with uc3906 for battery chargers and then after about 3 months, had problem with uc3906, this chip is burned in 3 times. I ask if this problem is common. I attachment my schematic circuit.

I charger battery 24 v at 1.6 amp and as pass transistor the TIP127 and Vin= 30v.

Maybe I have to migrate to BQ24450 or BQ24105.

best regards

over 11 years ago

0 Charles Mauney over 11 years ago

TI__Mastermind 31120 points

I do not see an issue with the schematic.

At the defined charge levels, it looks like the pass element is dissipation 10W which is quite a bit.

Is this raising the temperature of the IC. Is the IC the only component that is damaged.

You would probably benefit by going to a switcher.

0 Stachiotti Fernando over 11 years ago in reply to Charles Mauney

Prodigy 80 points

Thank you very much for responding quickly,

The power dissipated in the pass transistor is approximately P = Vce x I, 1.6A x 1.2V = 1.9V, approximately 2 Watt

I measured the base current demanded by the pass trasnsistor and does not exceed 25 mA, as shown in the datasheet.

I guess maybe some external element, storm or high input voltage could generate this problem.

I did the query just to make sure it has not happened to other people with the UC3906 and then consider his replacement, but I will continue testing with the UC3906.

Best regards

0 Charles Mauney over 11 years ago in reply to Stachiotti Fernando

TI__Mastermind 31120 points

Thank you for the reply. For the power dissipation, I was going off of the input of 30V and 24V cell.

I do not know of any known issues with the IC.

0 Stachiotti Fernando over 11 years ago in reply to Charles Mauney

Prodigy 80 points

Ok, Thank you for you information and help my. I going to continue testing with UC3906

Have a nice day Charles

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UC3906 burned