MPXM2102AS datasheet(484/670 Pages) MOTOROLA

484 / 670 page

AN1551

3–338

Motorola Sensor Device Data

www.motorola.com/semiconductors

The Motorola MPX2010 (see Table 1) is a calibrated and

temperature compensated, 10 kPa (full–scale), pressure

sensor device. The data sheet specifies a full–scale output of

25 mV at a 10 V supply voltage, for an applied pressure of 10

kPa. This same device can be pulsed at 40 V at a 10%

duty–cycle and produce either 100 mV for the same 10 kPa

pressure or 25 mV for only 2.5 kPa of pressure. This technique

allows a four–fold increase in the signal level for the rated

full–scale pressure of 10 kPa or the ability to maintain the

same signal level for a pressure that is four times lower (2.5

kPa).

Although the idea is relatively simple, the key to providing a

low–cost smart sensing solution is in both the hardware and

software implementation of this system. In the case of the

micropower application, having a “stand–alone” analog

sensing solution was a key criteria. As such, this design used

micropower op–amps, analog CMOS switches, gated timers

(one to control pulsed sensor excitation and one to control

sample–and–hold

function),

and

capacitive

sample–and–hold circuitry. The effect was a very low–current

drain, micropower sensor solution. Since low–power, rather

than low–pressure, was the driving design goal, errors

induced by power supply variation, temperature drift, and

device–to–device tolerances were not critical. Not that these

issues are not important for all applications, but for

low–pressure sensing, even small temperature drifts, device

parameter tolerances, and power supply variations cause

significant errors as a percentage of the sensor output signal.

should

apparent

that

the

“gated–timer

pulsing/sample–and–hold”

system

architecture

can

equally well employed to pulse at higher voltages for

increased sensitivity. However, a low–cost MCU can also

accomplish the functions of providing a control pulse to a

switching circuit (for the pulsed sensor excitation) and

affecting a synchronized sample–and–hold feature via

software control of an on–chip A/D converter. In addition, the

MCU has the capability to implement other “smart” features

that can lend the additional required accuracy and

functionality

desired

for

many

low–pressure

sensing

applications. The system design intended for low–pressure

applications, as well as the performance–enhancing features

of pulsed excitation for increased sensitivity, signal averaging,

software calibration, and software power supply rejection are

presented.

The

added

functionality

intelligent

communications capability and serial digital output flexibility

are also discussed.

Of course, these features lead to increased performance at

conventional, or even high–pressure ranges. Nonetheless,

these features have been developed in the context of

low–pressure sensing where the performance benefits are a

requisite of the application. Also, driving acceptance of this

system technology is a much easier task when coupled to

providing a sensing capability and level of functionality that is

otherwise not available in the industry today. Who would have

suspected that a viable smart sensing technology would have

resulted from the pursuit of addressing the low–pressure

sensing market? Significant pieces of this system solution are

protected intellectual property. Motorola holds several key

patents on using pulsed excitation for semiconductor sensors

and has filed several others regarding other portions and

future enhancements to this technology.

Table 1. MPX2010 Operating Characteristics (Supply Voltage = 10 Vdc, TA = 25°C unless otherwise noted)

Characteristic

Min

Typ

Max

Unit

Pressure Range

—

kPa

Supply Voltage

—

Vdc

Supply Current

—

6.0

—

mAdc

Full Scale Span (FSS)

Zero–Pressure Offset

–1.0

—

1.0

Sensitivity

—

2.5

—

mV/kPa

Linearity

–1.0

—

1.0

%VFSS

Pressure Hysteresis (0 to 10 kPa)

—

±0.1

—

%VFSS

Temperature Hysteresis (– 40

°C to +125°C)

—

±0.5

—

%VFSS

Temperature Effect on Full Scale Span

–1.0

—

1.0

%VFSS

Temperature Effect on Offset (0

°C to 85°C)

–1.0

—

1.0

Input Impedance

1300

—

2550

Ω

Output Impedance

1400

—

3000

Ω

Response Time (10% to 90%)

—

1.0

—

Temperature Error Band

—

°C

Offset Stability

—

±0.5

—

%VFSS

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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