1V regulator run from a single NiMH battery

There are loads of low dropout regulators which have a reference lower than 1.0V

What's wrong with something like a LP5952TL-1.0?

I would suggest a quick look through the likes of Digikey.

--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk

Ricoh R1100D101C LDO is an example:

Spec'd at a max dropout of 30mV at 1mA output. I think you will be fine at 1.2V.

Jon

By the way, Atmel's own eval kit for your very cpu uses that regulator. I don't use Atmel so I just went there and looked up the part for VDDBU on the BOM. Easy. You should have done that much:

As another poster mentioned, there are others as well. Do you design, professionally?

Jon

BTW, 1.2V is not a very conservative value for dropout with a NiMH cell, particularly if your product must handle low ambient temperatures. 1.1 or 1.05V would be better.

The Ricoh part that Jon mentioned has a worst case dropout voltage of

700mV at 1mA and 25°C (yes, the data sheet is misleading), so it could start to drop out at 1.724V in with 1mA load!, but, but at < 10uA it's _probably_ okay (up to you to check though). MOSFETs look like resistors, or better, so it should scale at least as well as 0.01mA/1mA * 700mV = 7mV.

Yes, I looked at the ricoh part, but the 700mV drop out put me off, it uses a 1,23V reference I think so I was not sure what would happen when Vin=3D1V. I will see if I can get one and try it, but surely it is dependent on the turn on threshold of the output Mosfet which is not defined. Atmel uses a 3V6 battery which gets round the problem. The national part has too high a quiescent current, more than the circuit uses Thanks again Thanks

Yes, I looked at the Ricoh part, it appears to have a 1.23V voltage reference so I wondered what would happen when the battery voltage dropped below the refernce, and below the turn on voltage of the output MOSFET, or does its still look like a resistor?