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MC33660 Supply Voltage — Parallax Forums

MC33660 Supply Voltage

PFloyd36069PFloyd36069 Posts: 135
edited 2014-07-10 14:02 in Propeller 1
Hello,

Just curious if I'm understanding this correctly. If I supply the MC33660 with 3.3v, does that mean I don't need a current limiting resistor between tx and the prop?

Datasheet: http://cache.freescale.com/files/analog/doc/data_sheet/MC33660.pdf

Thanks,
Bryan

Comments

  • abecedarianabecedarian Posts: 312
    edited 2014-07-09 23:05
    VDD is rated -0.3 <> 7.0 VDC.
    Logic is spec'd: high > 0.7 * VDD; low < 0.3 * VDD.
    CS high = > 0.7 * VDD; low =< 0.3 VDD.

    The 33660 transforms 5.0 V microcontroller logic signals to battery level logic signals and visa versa.

    Yes, it's a bit ambiguous, but I'd hazard the guess and assume that if the datasheet does not explicitly say it will work with 3v3 levels, which it does not say, it won't work properly without level translation proper.
  • Heater.Heater. Posts: 21,230
    edited 2014-07-09 23:35
    There is noting in that data sheet that indicates the device will work at 3.3v. The included example usage shows Vdd of 5V.

    So this calls for an experiment. See if it operates from the 3.3v supply.

    If it does, you are in luck. Else it looks like you need to arrange for a 5V supply for it and use that current limiting resistor on Tx.

    I'm curious, I have never heard of "ISO K Line". Do you really need that? Perhaps there are other ways to get a similar interface for the Propeller than use that chip.
  • abecedarianabecedarian Posts: 312
    edited 2014-07-10 01:09
    Heater. wrote: »
    I'm curious, I have never heard of "ISO K Line".
    K-Line is part of ISO-9141 / OBD diagnostics, similar to CAN and LIN.
  • Heater.Heater. Posts: 21,230
    edited 2014-07-10 01:44
    There is something new everyday around here.

    Also I have never seen the expression "battery level logic" before. Reminds me of the time as a kid I was running my 74 series TTL experiments off of a 12v motor cycle battery. It even worked...for a while.
  • PFloyd36069PFloyd36069 Posts: 135
    edited 2014-07-10 08:09
    OK, figured it couldn't hurt to ask :) I guess I'll just run I at 5v and use a current limiting resistor on the tx!

    Thanks,
    Bryan
  • abecedarianabecedarian Posts: 312
    edited 2014-07-10 14:02
    Note what I posted about the logic levels- logic high = 0.7 * VDD. So if VDD = 5v, logic high = 3.5, which depending on the voltage regulation the Prop may not be able to reach for sending data.
    However, there's the chance that the 33660 might just work with the Prop's outputs.
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