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PCB Layout Practices and Battery Power

paul miller44746
Intellectual 540 points
Other Parts Discussed in Thread: SIMPLICITI, CC2500, MSP430FG4618, TPS61097-33

Hey All,

 

I am working on a wireless application with the CC2500, MSP430 and Simpliciti.  I Had a few questions.

 

What is a sound practice for unused pins on a layout?  should I leave these floating, ground them, or use pull downs etc.  Board size is a critical aspect of this project.

What are the bare minimum components requred to use an MSP430?  (I amusing a msp430FG4168IPZ)

Anybody know a good battery (smaller the better) to use for such an application?  Preferably one with a holder that will allow for easy swapping of batteries?  I am using a TPS79933 (fixed 3.3V output) voltage regulator.  I looked around and most of the "coin" style batteries had very very low max current outputs, on the order of 5-10mA even if they lasted for a long time. 

Thanks

Paul

 

 

  • 0
    Expert 1790 points

    Hi Paul,

    I hope I can help you on your questions:

    Unused pins: TI recommends to use pulldown resistors on unused pins to avoid floating. Keep in mind that by default all unused Ports are set as input. However you can use the internal Pullup or Pulldown resistors (set by PxREN) to do the job. I recommend to add a small pad as testpoint for any SW debug purpose.

    Minimum components: On your MSP430FG4618 (I guess 4168 was a typo) you need a resistor and a capacitor on the reset pin and one or two filtering capacitors on the supply voltage. Have a look on "MSP430 Hardware Tools User's Guide" (SLAU278). It provides you good hints.

    Battery: TI used 2 x AAA battery on eZ430-RF2500T (3V). I use 2 x AAA NiMH accus on my design with USB charger circuit controlled by the MSP430. You may reduce the size futher by using a DC/DC converter e.g. TPS61097-33. Hence you need only one battery and get up to 200 mA.

    Regards

    Guenther

     

     

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