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Hi ! I'm trying to put a MSC1212Y5 in power down mode. Despite all I have tried, the uC continues to draw a current of about 0.2...0.3mA, like there is some internal block (analog or digital) that isn't turned off. I have already wasted 3 days, trying to solve the problem. Sometimes, I succeed to obtain a current of less than 1 uA, but this doesn't lasts too much (maybe minutes) and the current rises again to few hundreds of uA. Anyhow, the small current (under 1 uA) it is obtained only if I cut the analog VDD off. Otherwise (with AVDD = 4.5V) the current through the AVDD pin is 0.25mA with all analog blocks turned off. I have read all the application notes I have found: sbaa's, sbaaz's, sbyt's, errata's and so on...useless. Can somebody (please) help me, because I'm in a terrible lack of ideas and (what's the most important) TIME !
Dear Per, Thank you for your input. I'll try to answer to your questions: 1.If it is a known problem then it might benefits of a secret work-around since there are no errata dealing with it ! SBAS323 (revised in september 2005 from SBAZ001C) doesn't mention anything about this issue. The only (colateral) information is :" After a reset, bits IDAC0DIS and IDAC1DIS are set to 0, thus enabling IDAC0 and IDAC1. This behavior is not desired since the current DACs should be disabled after a reset. The proper default value for these two bits should be 1.". When I found it, all the sky went blue for me and I suddenlly relaxed: "so, that is!"...Well, it wasn't... 2.Words have value, so it is not recommended to waste them with explanations...When it comes to descriptions, the phrases are written in a "Nostradamus" manner: anyone is free to understand what it likes to. I have tried to keep AVDD at the same supply with DVDD, in order to be sure that RESET will find it right, either when active or afterwards. There is no influence on the further behaviour: there is no way to get a consumption under 250uA in the analog section of the uC (they say that if everything is off in this section, then the consumption from AVDD is under 100nA !). The only way to get rid of these 250uA is simply to turn off the AVDD (inspired from Alexander's Gordian Node :)). It is obvious that this leaves some parts unsupplied and this might "upset" something inside, but I have product to finish, I based the design on the datasheet specifications and, finally, I blew it ! I have had to do something... 3. I don't think so, but how knows? Anyhow, I made the other 4 sensors and the sollution proved to be reproductible...Until now... 4. I can't put everything in low state, since there are devices requiring high states, or inputs (like RXD0, or RXD1) which are driven by outputs. I couldn't spread three-state buffers all over the place, since there was a space limit (it should be a small sensor, not a factory...). But all port pins that supported low states during power-down were configured like this. I have followed the recommendations...Anyhow, this reffers to an eventual sittuation of shortenning some pins to ground; the behaviour is the same if you configure the port pins as CMOS-output and leave them high or low, or if you configure them as inputs and they are driven at correct low or high states. I am sure there is no input left floating or 8051-compatible driven low or written low. I have checked this for many days...
The only observation was that if I touched the floating AVDD pin (unsupplied), the DVDD current decreased. I have put the probe on the pin and saw what I expected to: a 50 Hz ripple, limitted around GND, at about +/- 300mV. Since putting AVDD at the correct voltage would yeld a consumption of 250uA, I thought that it might be useful to try suppling it with a negative voltage, as this might "unlatch" the "something" inside...(this is quite an academic kind of speaking...). It worked...but now I'm feelling like the researcher who cut the flea's legs, say it: "Jump!" and noted that "after <legoctomy> the flea is no longer hearing". Thanking you (and others) for your time, and waiting for suggestions, Gratefully Yours Adrian Moldovan