MCP1640 (need help)

Discussion in 'General Electronics Chat' started by DJ_Wat_Wat, Mar 16, 2013.

  1. DJ_Wat_Wat

    Thread Starter New Member

    Mar 14, 2013
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    I am new to this Circuit Forum.

    I am trying to find out information about MCP1640 IC because I want to use it as my power source for my circuits.

    I want to use it for 2 D-cell batteries also a 6V battery and 2 6V batteries to get 12V (I probably use a adjustable regulator to step it down) and get the output of 3.3V but application note only shows for voltage between 0.9V~ 1.7V and 3.0V to 4.2V.

    How about one from at least 5V to 0.9V?

    I posted an attachment of the datasheet.

    Thank you
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Your question is extremely confusing. It really helps if you make yourself clear.

    Is your question:

    "Can I have the MCP1640 regulate from 5V down to .9v"? Then the answer is no. It is a step up regulator not a step down.

    If you really want accuracy at .9 v I think you will need a voltage reference and not a regulator.
     
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  3. DJ_Wat_Wat

    Thread Starter New Member

    Mar 14, 2013
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    I'm sorry for the confusion.

    I am looking to see if I can use the MCP1640 for voltage range between 0.9V ~ 5V.

    How can I figure out the circuit for that type of range?

    I believe its has to do the resistors values in the voltage divider but I am not 100 percent sure.
     
  4. takao21203

    Distinguished Member

    Apr 28, 2012
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    You could use a 1 MOhm pot.
     
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  5. DJ_Wat_Wat

    Thread Starter New Member

    Mar 14, 2013
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    That's not a bad idea just play with it til I figure it out, I don't know why I didn't think of that before.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    If you want to use it with 5V in, your output voltage will have to be higher, but no higher than 5.5V. That's how I read the datatsheet.
     
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  7. DJ_Wat_Wat

    Thread Starter New Member

    Mar 14, 2013
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    If I am using 6V battery or a 12V battery (Two 6V batteries) I should just use a adjustable voltage regulator?
     
  8. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Read the datasheet. Unless I am wrong the MCP1640 is a boost regulator. The OP is starting with a higher voltage (if I am reading him right, his post is very confusing) not a lower one that needs to be boosted.
     
  9. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    It is going to depend on your application. What output voltage do you want?
     
  10. DJ_Wat_Wat

    Thread Starter New Member

    Mar 14, 2013
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    I want 3.3V 100 mA for my MCU but I have to use one 6 volts battery one product and two 6 volts batteries in other product.
     
  11. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Then you do not need an adjustable regulator. Look at the 34063. It is not the most efficient chip on the market but it has been around for years and there are tons of circuits out there for it. Plus it is very flexible, it will do step up, step down and polarity conversion depending how it is configured.

    The LM2675 from TI is another very easy to use chip and more efficient. The LM2675 is a 5V regulator but they have a 3.3V version too.
     
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