>> At these low voltages, the diode drop becomes significant. =A0Is the
>> diode a schottky?

Synchronous rectification.

> http://www.st.com/stonline/products/literature/ds/7320.pdf

>> 10uH sounds rather low unless you have a fast switching frequency,
>> probably around 1MHz or at least over 500KHz

No clock per se.
Terminates input ramp at 5 uS or 1A - seamless swap between PFM and
PWM as load varies.

> As pointed out, I missed the very obvious wattage comparison

Energy out per energy in, of which Wattage ratios are equivalent, is
the only meaningful efficiency measure. Current ratios and voltage
ratios depend on the boost voltage ratios and losses and more and so
by themselves give no indication of efficiency. IF you hold other
terms constant then the ratio of say 'output currents at constant Vout
for fixed power in' does give an indication of what's happening, but
this leads to such restricted measurement and setup situations that Vo
x Io / (Vin x Iin) is by far the best measure.

Be sure to measure Vin on the circuit side of any Iin ammeter.
Be aware that high frequency power supply noise on power wiring (in
and out) can play havoc with some meters). Largish cap (100 uF?)
across meter terminals can help.



              Russell

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