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130Re: [buildcheapeeg] changing the design for battery power and Irda

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  • Moritz v. Buttlar
    Feb 6, 2001
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      > The AT90S4433 has a absolute maximum rating for Vcc of 6.6V.
      > That means theoretically, if this voltage is exceeded only a fraction of a second
      > the chip will be damaged or lose permanently performance (i.e. more current uptake,
      > noise of the analog part etc.).
      > 1)Will it be guaranteed that with full loaded bateries the 6.6 V will _never_ be
      > exceeded ?
      > What happens, if someone uses rechargeable alkaline batteries instead of
      > NiCad-accus ?

      It depends on how failproof we want the design to be. If we write in the
      instructions that only rechargeable NiCd or NiMH cells are allowed than it would
      be completely safe.

      > 2)Another point is calibration voltage generation: It depends on stabilized Vcc.
      > However Vcal could be (with some circuit change) derived from the reference
      > voltage source.

      I think that would be better. It�s more stable as well.

      > BTW. How much voltage drop has a low drop voltage regulator and how much supply
      > current does it need ?

      That�s not the problem. It takes �A and needs a couple ov mV voltage drop. But
      most of these lowdropout regulators are in really tiny smd packages...

      > Irda data transmission should get a checksum (e.g. 16bit CRC) at the end of
      > each data block to check transmission quality.

      Yes, something like that has to be included.


      PS: TI offers free samples of INA114 (up to 8) for development engineers :)
      They are really friendly with samples now.

      Baltic Microsolutions / Flash Microcontroller Custom-Development
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