On Nov 26, 12:36*pm, Jeff Liebermann wrote:
On Fri, 25 Nov 2011 21:28:54 -0800 (PST),
wrote:



On Nov 25, 5:31*pm, "
wrote:
(...)
http://www.ti.com/lit/ds/symlink/tps62050.pdf
From the graph on the front page, it looks like n = ~35% *@ 15uA
output. *That's actually very good. *Thanks.

That's because of the 12uA typical quiescent current, where the chip
draws about the same current as the caliper load. *For equal currents,
that's 50% maximum efficiency. *The TPS62054 shows 50% efficiency at
2.7V in and 1.8V out (See Pg 8 Fig 4).

The chips do have a shutdown pin that cuts the quiescent current to
"less than 2uA". *Still high, but much better.

Yes, but, in the caliper context, who's going to turn the switcher
off, how, and when?

See the problem?

--
Cheers,
James Arthur