I don't understand what this means

Thread Starter

jimbarstow

Joined Nov 8, 2011
24
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
 

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praondevou

Joined Jul 9, 2011
2,942
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."
 

Thread Starter

jimbarstow

Joined Nov 8, 2011
24
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."
Yes, it is related. I really want to get that other circuit working. I hate giving up. This is for an alternative approach.
 
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