When trying to measure the efficiency of aTPS61201 DC/DC converter circuit using a multimeter, I am getting some hopelessly poor figures.
I am using the TPS61201 to provide a stable 3.3V from 2x AAA alkaline batteries to an ESP8266 based project which (when not in deep sleep) draws roughly 71mA most of the time but occasionally requires brief bursts of up to 240mA.
As far as I can tell, this is precisely the kind of application the TPS61201 was designed for and sure enough it supplies a beautifully stable 3.3V at the output. However, with a stable output current measuring 71mA and the PS pin pulled low I am seeing an input current of 660mA for a 2.4V input (via bench PSU). This can't be right. I was expecting to see something more like 120mA under these conditions.
Assuming my circuit was to blame, I bought some ready made TPS61201 based boards (Pololou U1V10F3) for comparison, but I'm getting virtually identical results from them.
I have simplified the vreg circuit to its bare essentials, connecting VOUT to GND on the U1V10F3 board via a few resistors in parallel to create a load such that the output current measures 105mA, yet I'm still measuring 660mA ish on the input side. When I bring the output current down to 25mA, the input current hardly changes.
I can only assume I'm doing something silly when measuring the input current wrongly somehow. I think the TPS61201s power save mode may be implicated. Any explanation / tips at all?
