I don't understand what this means

Discussion in 'General Electronics Chat' started by jimbarstow, Dec 12, 2011.

  1. jimbarstow

    Thread Starter New Member

    Nov 8, 2011
    I may be using a pressure sensor from freescale for a project but I don't understand 2 things in the datasheet.

    1. The sensor has 6 pins and it isn't clear how 3 of the pins are handled. I'd be using the 2 port version described on page 10. Pins 1-3 are simple (Vout, gnd, and Vcc). Three of the other pins are designated for "V1", "V2", "Vex" but the datasheet doesn't define what those are. I found an example which used a similar sensor with a similar spec (from freescale) and these pins were left unconnected. Are V1, V2, and Vex standard names? Should I know what they are? Can I ignore them like in the example I found?

    2. the data sheet describes how the sensor should be decoupled via capacitors. The input voltage has 2 capacitors on it, one 1 μF and the other 0.01μF in parallel. Why 2 capacitors of such different sizes? Does this pattern somehow smooth different kinds of fluctuations?

    I've attached 2 images. One shows the info for #1 and the other for #2
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    Is this related to your other pressure sensor thread?

    In another datasheet it says:

    "Pins 4, 5, and 6 are internal device
    connections. Pin 1 is noted by the notch in
    the Lead. Do not connect to external
    circuitry or ground."

    From Wikipedia:

    "Since capacitors differ in their high-frequency characteristics (and capacitors with good high-frequency properties are often types with small capacity, while large capacitors usually have worse high-frequency response), decoupling often involves the use of a combination of capacitors. For example in logic circuits, a common arrangement is ~100 nF ceramic per logic IC (multiple ones for complex IC's), combined with electrolytic or tantalum capacitor(s) up to a few hundred μF per board / board section."
  3. jimbarstow

    Thread Starter New Member

    Nov 8, 2011
    Yes, it is related. I really want to get that other circuit working. I hate giving up. This is for an alternative approach.