Problem applying a mosfet

Or just use a Schmitt oscillator and a LAN transformer or something else that can step it up.

Oh, I'm sorry, my mistake, I forgot about that. The '7660 has been a longtime favorite of mine, but that's generally the way I use it. Analog Devices makes the ADM660 as an improved 7660, and show it used as a doubler: Apply the input voltage to the GND pin and OUT connected to GND. Then use V+ as the output. Neat, huh! However, low-voltage performance is compromised: "Input voltages from 2.5 V to 7 V are allowable." Too bad about that 2.5V limit. Oh, one other thing, connect LV to gnd.

I've heard this scheme works with all the 7660 variants. In this mode, ICs are running from their outputs, which being 2x higher than the input, means they can be used down to battery input voltages below the specs, provided they got started when the battery was fresh and at a higher voltage.

NSC preaches this connection scheme for their LM2662. The max1682 was designed as a doubler, and they say their chip starts down to 2 volts.

So somebody should start making combo charge pump boosters and gate drivers.

John

That looks like a winner to me

Ah, here's a good choice, NSC's LM2767 doubler, starts at voltages down to 1.8 volts, draws 10uA, sot-23 package, in stock for $1.11 ea at DigiKey.

Yes, quite a few of these exist already, e.g. LTC's LTC1154, 1155 and 1156, which drive one, two or three mosfets, resp, but most of these are meant for 5V supplies, etc., e.g. the 4.5V min spec for the LTC115x series.

LTC does have the LTC1157 operating to 2.7V, but what's needed are new designs meant for use with single cells.

All this stuff is expensive and often single-sourced. An alternative would be to generate a higher voltage using a JFET oscillator that works down to a single cell voltage at the end of its discharge curve. Then use "real" logic to drive the devices.

Agreed. Gets easier to wrap some wire through a ferrite bead and make a single transistor boost supply.

If you are lucky you can find an AM IF coil that is tapped off at a convenient ratio, or use a modem transformer. But I did get quite good at winding small stuff. In 3rd grade we participated in the knitting classes for girls because our school did not have a shop.