Current monitor max "vout" = ?

[eem2am]

Hello,
This concerns single supply operation of LT1787 as in figure 8, page 12 of the datasheet.
The LT1787 current monitor, on page 3 of its datasheet quotes "vout" as "v(bias) + 1.024V" if "Vs+ > 3.3V".

Why does "Vs+" have to be greater than 3.3V?

Surley LT1787 can produce vout = v(bias) + 1.204V if "VS+" = 2.5v?
(assuming v(bias) = 0V.

Further down the page on page 3, "VOmax" is stated as VS+ -0.75v.

So why are they saying that "vs+" has to be greater than 3.3V for "vout" to be 1.024V?
Surely if "Vs+" is just 2.5v, then "vout" could be 1.024V ?

LT1787 DATASHEET:
http://cds.linear.com/docs/en/datasheet/1787fc.pdf

 

[(*steve*)]

I can't say why, but they are telling you that.

Perhaps the generation of the internal reference voltage requires a little over 2V of headroom?

Perhaps you could do your own tests to see if it works at a lower voltage.

 

[eem2am]

I am wondering if its actually possible for "vout" to be 1.024V if "vs+" is just 2.5V.

I see your point, but even if I order one and it does give vout=1.024v at vs+=2.5v, -if the datasheet doesn't corroborate this, then i'll be worrying if the next batch of LT1787 will behave so well?

 

[(*steve*)]

then i'll be worrying if the next batch of LT1787 will behave so well?

Exactly.

And that's why you stay within specified limits. You have a far higher degree of certainty that what works will work next time.

 

[eem2am]

I am just wondering what is the guaranteed maximum achievable value of "Vout" if "vs+" is just 2.5v?