MPXHZ6116A Output Loading

[tonysz]

Hello,

I am reviewing a design in which the output of a MPXHZ6116A pressure sensor is being loaded with a 10nF capacitor to GND.

This value of capacitor is significantly larger than the 47pF shown in the data sheet's "Figure 3. Typical Applications".

I have no experience working with pressure sensors but have a concern that this greater capacitance may have an undesirable effect on the performance the sensor.

What effect(s), if any, could this 10nF load have on the performance of the MPXHZ6116A?

Thank you.

[Joshevelle]

Hello Tony,

In the datasheet, page 4, figure 3 shows the typical application circuit for "Output Source Current Operation"  it shows a parallel RC  circuit with a 47pF capacitor and a 51Kohm resistor. This kind of circuit does not act as a filter, unless feed with a current source. Being honest I don't really know why is that circuit recommended for the I MPXxx6116A, I would need to investigate further. However, I would highly recommend you to use a low pass filter instead.

You mentioned a 10nF capacitor, do you also have a resistor? as long as the low pass filter has a cut off frequency of 650Hz, you shouldn't have any problems. Please take a look at the following application note, it contains all the required information to properly filter the output voltage of our pressure sensors:

"Noise Considerations for Integrated Pressure Sensors":

http://cache.freescale.com/files/sensors/doc/app_note/AN1646.pdf

Hope it helps!

Josh