Am So 20. April 2008 schrieb Werner Almesberger: > [EMAIL PROTECTED] wrote: > > with standard battery we get a standby of 1200 / 0.6 = 2000h max. Sounds quite > > neglectable, but like Andy said, every bit of current counts. It's all > > summing up. > > Whoa, that's the MPU going full blast all the time. [EMAIL PROTECTED], here > we come ;-) > > If the MPU can sleep every once in a while, we get a low-power mode > that's about three orders of magnitude more battery-friendly.
So maybe we really just don't care about the full power up consumption of MPU? Probably it's just not worth the additional effort. > > > We can handle this. Have the MPU at some booster that's to be leveled down > > from e.g. 3.0V default to sth like 1.8V, what is task of the MPU to set up > > PMU. > > Yeah, with an LDO, we'd just burn the power elsewhere, so it should > be a switching supply if we really care about power consumption there. > Not sure if there's anything really nice and small out there, though. > > Maxim have a bunch of boost converters that don't look too bad, e.g., > the MAX867EUA+T [1] (3.3V, 3x5mm footprint). Needs external caps, > inductor, and diode. > > The tiniest I could find is the TI TPS62700YZFR [2] (3.09V or > adjustable 1.6x1.5mm), which doesn't even need an external diode. But > it's not cheap, and it burns 300uA on its own, basically negating any > gains we could get. > > [1] http://datasheets.maxim-ic.com/en/ds/MAX866-MAX867.pdf > [2] http://focus.ti.com/lit/ds/symlink/tps62700.pdf > > > All the other chips will have additional FET-low-R switches (one for > > each powerline that need it) to protect them from OV Missunderstanding: I'm talking about OverVoltage protection, until PCF50633 is settled for correct booster output, not to burn chips. No 0Volt > > I don't think the PCF50633 ever pulls strongly to GND. It normally > uses a weak pull down if the regulator is off, though. > > > Some VoltageDetection for PowerGood if we can spend. > > So far, we got away with what's inside the PMU :-) Yea but hat was original concern about bad defaults of PCF50633, so it's good to have a MPU... /j
