In September 2008 (!) Bon Ammerman said

> I am looking for step-up switcher with following characteristics:
>
> 1: Input voltage: 1 alkaline cell, the lower the starting voltage and
sustain voltage the better.
> 2: Output voltage: 5V
> 3: Current: max of 500ma (yes, I know this will kill the input cell pretty
quickly)
> 4: Efficiency: not critical, 80% nice
> 5: Through hole mounting
> 6: Reasonable cost: In 100's total cost of circuit, including switcher,
inductor, cap(s), diode under $2.00 if possible
> 7: Soft failure would be nice: ie: if it can't produce a full 5V on output
given the source impedence then generate what it can.
> Can be IC or discrete solution.

Did you find a good solution to that requirement.
It closely matches one that I now have.
While I have a number of potential solutions it would be interesting
to know what you ecided.

A good candidate is the ON Semi NCP1450 with external switch
transistor and recitifer.
Stupid choice of making Vsense and Vdd same pin makes programmed
voltage out harder.
They have a spare pin (use 4 i SOT23-5 pkg).
Efficiency is largely in the designers hands,.
Switch, inductor and diode make the major difference.
FET well under 100 milliohms Rdson is needed.
(Rule of thumb = 200% losses per ohm)
Inductor under 100 milliohms is needed.
(ROT: 150%/ohm)
Schottky dioe is OK but gives significant loss.
(ROT: 40 x Iout / Pout % loss)
Synchronous output rectifier will help if $ allows.
Digikey $US0.25  in volume and not much more in lower quantities.

Chinese sourced CE6360 seems to be a pin compatible replacement.
getting a (good) data sheet is problematic.
Prices liable to be 1/2 - 1/3 Digikey in volume.

Other more integrated NCP14xx fade in power out max at lowest Vin.

TI UCC3941 is good but limited by being highly integrated.

NCP1422 is excellent - not sure if it operates at quite as low Vin as i
need.

Zetex ZXSC100 also promisiong.
Same principle as NCP1450 BUT also has a low side switch current sense
with 17 millivolt (!!!!) sense voltage.
Nice addition.

What you used would be of interest.

Some Asian designs that I have seen use CE6360 ~= NCP1450 but do not
realise potential efficiency due to compromise design choices.



                  Russell
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist