Analog-to-Digital Converter - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 625

Characteristic Min. Typ. Max.

Pressure range
Zero pressure offset
Full-scale span 2
Output at FS pressure
Combined pressure non-linearity and pressure
hysteresis 3
Temperature effect on span 4
Temperature effect on offset 4
Response time (10% 2 90%) 5
Repeatability

0 psia
0.205
4.455
4.660
—

—
0.250
4.500
4.750
6 0.1

30 psia
0.295
4.545
4.840
6 0.5

6 0.2
6 0.2
0.1
6 0.05

6 1.0
6 1.0
—
—

—
—
—
—

1 Reference conditions: TA = 25°C, supply voltage V S = 5 V
2 Full-scale span is the algebraic difference between the output voltage at full-scale pressure
and the output at zero pressure. Full-scale span is ratiometric to the supply voltage.
3 Pressure nonlinearity is based on the best-fit straight line. Pressure hysteresis is the
maximum output difference at any point within the operating pressure range for increasing
and decreasing pressure.
4 Maximum error band of the offset voltage or span over the compensated temperature
range, relative to the 25°C reading.
5 Response time for 0 psi to full-scale pressure step response.
6 If maximum pressure is exceeded, even momentarily, the package may leak or burst or the
pressure-sensing die may burst.

Table 12.12 ■ ASCX30AN performance characteristics 1

Pin 1: external offset adjust
Pin 2: V S
Pin 3: V OUT
Pin 4: GND
Pin 5: N/C
Pin 6: N/C

ASCX30AN

1 2 3 5

4 6

Figure 12.21 ■ ASCX30AN pin assignment

Example 12.11
▼ Describe the circuit connection of the ASCX30AN and the voltage level shifting and
scaling circuit, and write a program to measure and display the barometric pressure in units
of mbar.
Solution: The circuit connection is shown in Figure 12.22. The circuit in Figure 12.22 will shift
and scale V OUT to the range of 0,5 V. According to Table 12.12, the typical value for the offset
adjustment is around 0.25 V and can be achieved by using a potentiometer.