PICLIST -- Yesterday, Mike Harrison wrote: / . . . /What I want to know is what's the lowest possible power consumption /in sleep, lcd on, 3.6v, WDT off, INCLUDING the lcd (small, 40x30mm, / . . . /I assume the 32K t1 osc is the lowest power, and it can be used to /wake the CPU every sec. or so. In my app, sleep current dominates - avarage current when awake will add about 1uA (awake 1ms per sec at /4MHz). /The data sheet gives values for LCD voltage generation, but NOT the /LCD module on its own, i.e. with external voltage generation, and /gives no clue about typical power draw of the LCD itself - obviously /this is panel dependent, but a rough guide (e.g. power vs. capacitance /or a couple of specific displays) would have been nice. / /Has anyone measured the supply current in a real app ? /I'd like 15-20uA max - anyone know is this realistic ?=20 / . . . _/ L_/ Mike Harrison / White Wing Logic / wwl@netcomuk.co.uk _/ L_/ _/ W_/ Hardware & Software design / PCB Design / Consultancy _/ W_/ /_W_/ Industrial / Computer Peripherals / Hazardous Area /_W_/ and then Chris Eddy replied: /As luck will have it, I am on a project that is almost exactly like yours. /It has a 1.2M crystal, a 32K crystal on the T1 line, a static LCD like you /mentioned, and it runs on 3V. Our initial prototype with fully functional /software draws the following values. In fully awake mode, without buzzer or /backlight on, it draws 430uA. In semi-sleep (T1 wakes every half second, /I'm prestuffing the timer) I measure 89uA. In full sleep (in which I turn /off the LCD) I measure between 1 and 2 uA. (Hello? check that meter /again?) Keep in mind that every time we turn a peripheral on or off in /sleep, these numbers seem to change somewhat. Word of caution, there are /conflicting acounts of how to hook up the LCD voltage pins, I tie the top /two together but not to VCC (If you do it works, but drives suddenly to the /mA range), and tie the bottom two together. Remove the contrast adjustment /for static LCD's. Compare your datasheet with the PICDEM3 users guide to /get a bigger picture. Watch all of your externals to ensure that you don't /hog current. Use external chips that claim super low shutdown current. And /for God's sake, use low leakage caps in your supply, lest you leak more than /you use. Electrolytics are not very good. / /Chris Eddy /Pioneer Microsystems, Inc. to which Mike answered: /Oh, dear, looks like I'll have to look elsewhere to get that 10 year /life from a 1AH battery, then! /This figure seems a little high - I recently did a product with an /Epson LCD chip, with 4:1 mux (presumably more power hungry), which /took about 40uA at 5V.=20 Here's my two cents worth: I'm doing a 3V app with a 16C54A that sleeps 99.9% of the time. WDT off. The databook says average drain should be about 1 microamp. Using 2 alkaline button cells @ 190 mah. 190 milliamp-hours is 190,000 microamp-hours, so at 1 microamp they should give me 190,000 hours, or about 20 years, eh? I'm in the process of measuring this, but don't fully trust my instrumentation. How do I a test for ten-year life in less than ten years? -- Mel Evans mevans1027@aol.com 313-747-7196 I'm doing a 3V app with a 16C54A that sleeps 99.9% of the time. WDT off. The databook says average drain should be about 1 microamp. Using 2 alkaline button cells @ 190 mah. 190 milliamp-hours is 190,000 microamp-hours, so at 1 microamp they should give me 190,000 hours, or about 20 years, eh? I'm in the process of measuring this, but don't fully trust my instrumentation. How do I a test for ten-year life in less than ten years? -- Mel Evans mevans1027@aol.com 313-747-7196