MPXY8300 datasheet(79/164 Pages) FREESCALE

79 / 164 page

MPXY8300 Series

Sensors

Freescale Semiconductor

The signal conditioning of the pressure sensor begins with a capacitance to voltage conversion (C-V) followed by a switched

capacitor amplifier. This amplifier has adjustable offset and gain trimming that is set by the trim register. The micro-machined

pressure transducer, C-V converter, sample-and-hold, buffer and trim registers are on the separate P-Chip silicon device

mounted within the MPXY8300 Series package.

The MCU contains four registers of control, status and trim bits. In addition the P-Chip is powered up through the general purpose

I/O driver. The proper sequencing of these bits are handled by the REIMS_READ_COMP_PRESSURE firmware subroutine

described in Section 14.

The output values of $000 or $1FF from the calculated pressure measurement are considered fault codes. Further, any calculated

value of pressure below minimum calibrated range or above the maximum calibrated range will be converted to the $001 or $1FF

codes respectively. The transfer function for pressure versus an 9-bit result from the REIMS_READ_COMP_PRESSURE

firmware depends on the calibrated range of the device.

For the 100-450 kPa range the transfer function is:

For the 100-800 kPa range the transfer function is:

For the 100-1500 kPa range the transfer function is:

NOTE

The accuracy, power consumption and timing specified for a pressure measurement in the electrical

specifications in Section 17 are only guaranteed if the user obtains a pressure reading using the firmware

subroutine call, REIMS_READ_COMP_PRESSURE.

Faults in the pressure sensor that result in a reading less than the minimum level or greater than the maximum calibrated level

will result in the firmware making the output value zero. An output code of zero or 255 are considered fault codes.

Another cross check is that can be performed is that there should be a change in pressure in the presence of a change in

temperature. Therefore the user software should cross check the pressure and temperature readings to determine if the device

is responding to the Ideal Gas Law:

The temperature within a tire will rise after the tire has been in motion for some period of time. This rise in temperature should

be accompanied by a rise in pressure. Lack of this pressure rise may be an indication of a plugged pressure port or damaged

pressure sensing diaphragm.

NOTE

The triggering of the ADC10 is shared with the ACI for the acceleration measurements. Both a pressure

measurement and acceleration measurement cannot be started before the ADC10 is triggered as there is no

status bit to define whether the PCI or the ACI triggered the reading that was captured and converted by the

ADC10.

0.686

CODE

99.314

1.375

CODE

98.625

2.751

CODE

97.250

MPXY8300 Datasheet(PDF) 79 Page - Freescale Semiconductor, Inc

MPXY8300 Datasheet(HTML) 79 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL