TPS76801 Vin minimun question.

Bryan Busacco

The product folder for the TPS76801 states: TPS76801 Status: ACTIVE
Single Output LDO, 1.0A, Adj.(1.5 to 5.5V), Low Quiescent Current, Fast Transient

When I click on the datasheet the Q datasheet opens and states that the minVin = 2.7v.

I think this is actually the Automotive datasheeet being found in the product folder for the non-automitove device?

I explored the web and can not find a TPS76801 datasheet that descrived Vin as 1.5v to 5.5v.

Link: http://www.ti.com/product/tps76801

Datasheet found at the above link: http://www.ti.com/lit/ds/symlink/tps76801.pdf

Please help.

Thanks,

Bryan Busacco

over 13 years ago

0 Bill Stokes over 13 years ago

TI__Expert 8890 points

Hi Bryan,

I have not discovered why this part is labeled "Q". Perhaps one of the automotive guys can fill us in. Unfortunately, that "1.5V - 5.5V" is referring to the "adj" output voltage range.

Regards

Bill

0 Sureena Gupta over 13 years ago

TI__Intellectual 1130 points

Bryan,

If you notice the TPS76801 datasheet says TPS768xxQ and not TPS76801-Q1. The Q at the end (just an old way of listing parts in 1999 - old days) is different from Q1 (automotive qualification). An another example would be TPS7301Q is it not an automotive device and was created in 1995 (revised 1999).

DS for non automotive TPS76801: http://www.ti.com/lit/ds/symlink/tps76801.pdf

DS for automotive TPS76801-Q1: http://www.ti.com/lit/ds/symlink/tps76801-q1.pdf

Please feel free to ask me any questions you may have.

BR,

Sureena Gupta

Product Marketing Engineer

0 Bryan Busacco over 13 years ago in reply to Sureena Gupta

Expert 1215 points

The non Q1 device states Vin min as 2.7v.

In the following application can this device safely be used ( even though we are below Vin Min by 200mV?

Vin = 2.5v

Vo = 1.8v

Io = 100mA and max 1A output current.

Thanks, Bryan.

0 Jeff F over 13 years ago in reply to Bryan Busacco

TI__Guru**** 166626 points

The device will not be damaged at Vin=2.5V but it may be able to provide higher currents, approaching the 1A max, and maintain regulation because it was not tested for input voltages below 2.7V. I recommended moving to TPS7A8001.

0 Bryan Busacco over 13 years ago in reply to Jeff F

Expert 1215 points

We are kinds stuck because the board is layed out. Hoping we can live with the discrepency. A redesign will certainly occur.

Note that typically the output could be as low as VREF. In this case VREF is about 1.1834 or about 1.2V. If max voltage drop is about 300ma (for 1A current), then, the input could be as low as 1.5V (unless some internal design issues require higher input voltage).

Thanks,

Bryan.

0 Bill Stokes over 13 years ago in reply to Bryan Busacco

TI__Expert 8890 points

Hi Bryan,

The part was characterized for the data sheet to meet all specifications with the Vin as low as 2.7V. Now, as Jeff says, the part will likely work at Vin=2.5V. But, at some point likely not much lower than 2.5V the internal control circuitry of the part will start to shut down. I am confident that the LDO will be off long before Vin falls to 1.5V.

Regards

Bill

0 Bryan Busacco over 13 years ago in reply to Bill Stokes

Expert 1215 points

Yes, as expected.

More a matter of curiosity at this point. It looks like 2.5 is going to work short term. and the TPS7A8001 is the right choice for a redesign.

Bryan.

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TPS76801 Vin minimun question.