MPXM2102AS datasheet(566/670 Pages) MOTOROLA

566 / 670 page

AN4010

3–420

Motorola Sensor Device Data

www.motorola.com/semiconductors

Table 1 shows the jumper settings for both analog and

switches outputs.

Table 1. Output Jumper Settings

Output

JP4

JP5

JP6

JP7

Analog

Out

Switch

Out

For the switch output option, it is desirable to apply some

hysteresis on the output signal to make it relatively immune to

potential noise that may be present in the voltage signal as it

reaches

and

passes

the

threshold

value.

This

accomplished with feedback resistor R10.

From basic

op-amp theory, it can be shown that the amount of hysteresis

is computed as follows:

VH = Vout *[1–(10 / ( R10 + R pot-eff))]

Where:

–VH is the output voltage attenuation, due to hystere-

sis, in volts

– Vout is the output voltage (railed hi or low)

– R10 is the feedback resistor, = 50K

– Rpot-eff is the effective potentiometer resistance

VH may vary depending on the particular value of the

potentiometer.

Figure 5a. Output Transition without Hysteresis

Figure 5b. Output Transition with Hysteresis

To take an example, suppose that the supply voltage, Vs is

5 volts, and the threshold is set to 60 percent of Vs, or 3 volts.

This corresponds to one leg of the 1K potentiometer set to

0.4K while the other is set to 0.6K. Thus the effective pot

resistance is 0.4K // 0.6K = 0.24K.

Therefore,

VH = 5V* [1– (50K/(50K + 0.24K))] = 24 mV.

Under these conditions, V signals passing through the

threshold will not cause Vout to oscillate between Vs and

Ground as long as noise and signal variations in V are less

than 24mV during the transition.

Figure 5. Illustrates the

benefit of having a hysteresis feedback resistor.

GAIN CUSTOMIZATION

The low-pressure evaluation board comes with default

gains for both G1 and G2. G1 is factory set at 101, while G2

is set to 1. Jumpers JP1, JP2 and JP3 physically connect the

resistors that produce these default gains. Three resistor

sockets (R11, R41 and R51) are provided in parallel with R1,

R4 and R5, respectively. By removing jumpers JP1,JP2 and

JP3, and soldering different resistor values in the appropriate

sockets, different gain values can be achieved. The limit on

the largest overall gain that can be used is determined by

op–amp saturation. Thus if gain values are chosen such that

the output would be larger than the supply voltage, then the

op–amp would saturate, and the pressure would not be

accurately reflected. Table 2 outlines the jumper settings for

customizing the gain.

Table 2. Resistor and Jumper Settings for Gain

Customization

Gain

Resistors

Jumpers

Remarks

R11

R41

R51

JP1

JP2

JP3

101

load

Default

User

Set

load

Out

R11=R41

101

User

Set

load

Out

User

Set

User

Set

load

Out

R11=R41

DESIGN CONSIDERATIONS

Since the evaluation board is primarily intended for

low–pressure gage and differential applications, large gain

values can be utilized for pressures less than 1.0 kPa. For

example if G1 is set to 101, and G2 set to 6, then the total gain

is 606.

Inherent in the MPX2010 family of pressure sensors is a

zero-pressure offset voltage, which can be up to 1 mV. This

offset is amplified by the circuit and appears as a DC offset at

Vout with no pressure applied. The op-amp also has a voltage

offset specification, though for the recommended op-amp this

value is small and does not contribute significantly to the Vout

offset.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

MPXM2102AS Datasheet(PDF) 566 Page - Motorola, Inc

MPXM2102AS Datasheet(HTML) 566 Page - Motorola, 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