MPXM2102AS datasheet(567/670 Pages) MOTOROLA

567 / 670 page

AN4010

3–421

Motorola Sensor Device Data

www.motorola.com/semiconductors

For example, if the evaluation board is being used under the

following conditions:

Vs = 3V

G1 = 101

G2 = 6

MPX2010 zero pressure offset = 0.3mV

At this supply voltage, VOFFSET can be calculated to be

6.7% x 3V = 0.2V.

The voltage V, due simply to the zero

pressure sensor offset voltage of 0.3mV, can be calculated

from equation (1):

V1 = 0.3mV * 101 + 0.2V = 0.23V

The voltage after the second gain stage comes from

equation (2),

V2 = 6 x 0.23V = 1.38 V.

Therefore, before any pressure is applied to the sensor, a

1.38V DC signal will appear at V. Since the supply voltage is

3V, the available signal for actual pressure is 1.62 V. With a

total gain of G1 x G2 = 606, the largest raw pressure signal that

can be accurately measured would be 1.62V/606 = 2.67 mV.

For the MPX2010 family operating at Vs = 3V, this

corresponds to roughly 3.5 kPa.

The board lends itself well to system integration via an A/D

converter and microprocessor. For particular applications,

general knowledge of the expected pressure signal can aid in

choosing the proper customized gain. This will avoid op-amp

saturation and will also ensure that the full-scale output signal

is suitable for A/D conversion. To take another example,

suppose that a particular application has the following

constraints:

Supply Voltage, Vs = 5.0 V,

(thus VOFFSET = 6.7% x 5 = 0.335 V)

Sensor zero–pressure offset voltage, VZP = 0.3mV

Expected Pressure range = 0—2 kPa,

(corresponds to

DVSENSOR-MAX = 2.5mV @ 5V)

Desired maximum output range,

DV2MAX = 2V

(assume VMIN = 2V, V2MAX = 4V for reasonable A/D

resolution)

By manipulating equations (1) and (2) it can be shown that,

DV2MAX = GT x DVSENSOR–MAX

where GT is the total gain, equal to G1G2.

Thus GT = 2V/2.5mV = 800

To find G1 and G2, evaluate V2MIN at the zero pressure

condition.

V2MIN = G2 V1MIN,

But V1MIN = G1 VZP + VOFFSET

Thus V2MIN = GT VZP + G2 VOFFSET

Solving for G2, G2 = (V2MIN – GT VZP)/ VOFFSET

numerically, G2 = (2V — (800x.0003V))/.335V

G2 = 5.2, and G1 = GT /G2 = 152

BOARD LAYOUT & CONTENT

The low-pressure evaluation board has been designed

using standard components.

The only item that requires

careful selection is the operation amplifier IC. Because the

selected gain may be relatively high as in the previous

example, it is essential that this device have a low offset

voltage. A device with a typical voltage offset of 35 mV has

been selected. Even with a gain of 1500, this will result in a

52mV offset. Table 3 is a parts list for the board layout shown

in Figure1.

Table 3. Parts List

Ref.

Qty.

Description

Value

Vendor

Part No.

Pressure Sensor

10 Kpa

Motorola

MPX2010

MPXC2011

Vcc Cap

1 uF

Generic

Op-Amp Cap

0.1 uF

Generic

2nd stage cap

4700 pF

Generic

LED

Generic

for U1

Op-Amp socket

Generic

Op-Amp

Analog

Devices

OP496GP

R1, R4

1/4 W Resistor

100K

Generic

R2,R3,

R5,R6

1/4 W Resistor

Generic

1/4 W Resistor

6.8K

Generic

1/4 W Resistor

510

Generic

Potentiometer

Bourns

3386P–102

R10

1/4 W Resistor

51K

Generic

R11

1/4 W Resistor

custom

Generic

R12

1/4 W Resistor

Generic

R41

1/4 W Resistor

custom

Generic

R51

1/4 W Resistor

custom

Generic

JP1 –

JP7

Jumper

Generic

3 Pos Connector

Phoenix

MKDS1

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

MPXM2102AS Datasheet(PDF) 567 Page - Motorola, Inc

MPXM2102AS Datasheet(HTML) 567 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