DA6502.008

29 November 2012

14 (20)

APPLICATION INFORMATION

Input Signal Range Definitions

The input signal voltage polarity is from positive input PI to the negative input NI. MAS6502 has input signal

range (ISR) and offset (OFFSET) selection options that determines the input signal range of the A/D converter.

The minimum and maximum input signal values in the linear input signal range (ISRLIN) are calculated as

follows.

2

_

ISRLIN

OFFSET

V

MIN

IN

−

=

Equation 1.

2

_

ISRLIN

OFFSET

V

MAX

IN

+

=

Equation 2.

Table 11 shows minimum and maximum input signal values in the linear input signal range at different input

signal range and offset selection combinations.

Table 11. Minimum and maximum input signal values in the linear input signal range

OFFSET

ISR

ISRLIN

VIN_MIN

VIN_MAX

[mV]

[mV]

[mV]

[mV]

[mV]

0

325

260

-130

130

33

325

260

-97

163

0

220

176

-88

88

33

220

176

-55

121

0

150

120

-60

60

33

150

120

-27

93

0

100

80

-40

40

33

100

80

-7

73

The digital A/D conversion result, CODE, depends on the input signal as follows.













⋅

−

+

⋅

=

ISR

OFFSET

V

CODE

CODE

IN

MAX

5

.

0

Equation 3.

CODE = digital A/D-conversion output code

Pressure Measurement Configuration

Piezoresistive absolute pressure sensor can be modeled roughly with following signal voltage characteristic

when including only first order pressure and temperature characteristics..

(

)

(

)

(

)

(

)

(











−

⋅

+

⋅

+

⋅

−

⋅

+

⋅

⋅

=

REF

OS

FS

REF

FS

REF

IN

T

T

TC

OS

p

p

T

T

TC

FS

VDD

VDD

T

p

V

1

1

,

Equation 4.

VDD = supply voltage

p = pressure [bar]

FS = full-scale span [V]

OS = zero pressure offset [V]

T = actual temperature to be measured [°C]

The above linear approximation includes sensor full-scale span and offset signal temperature dependencies.