DA6503.005

14 December 2016

25 (34)

APPLICATION INFORMATION

Input Signal Range Definitions

The input signal voltage polarity is from positive input PI to the negative input NI. MAS6503 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. Due to ratiometric principle the input signal range is directly proportional to VDD.



















2

7

.

2

_

ISRLIN

OFFSET

V

VDD

V

MIN

IN

Equation 1.



















2

7

.

2

_

ISRLIN

OFFSET

V

VDD

V

MAX

IN

Equation 2.

Table 13 shows minimum and maximum input signal values in the linear input signal range at different input

signal range and offset selection combinations.

Table 13. Examples of minimum and maximum input signal values in the linear input signal range (Vdd=2.7V)

OFFSET

ISR

ISRLIN

VIN_MIN

VIN_MAX

[mV]

[mV]

[mV]

[mV]

[mV]

0

373

298

-149

149

126

373

298

-23

275

0

253

202

-101

101

86

253

202

-15

187

0

172

138

-69

69

57

172

138

-12

126

0

115

92

-46

46

40

115

92

-6

86

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



















ISR

OFFSET

V

CODEFS

CODE

IN

5

.

0

Equation 3.

CODE = digital A/D-conversion output code

CODEFS = A/D-converter maximum code (minimum code is zero)

See page 4 Electrical Characteristics for CODEFS values at different over sampling ratio (OSR) selections.

Pressure Measurement Configuration

A piezoresistive absolute pressure sensor can be modeled roughly with the 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

sensor parameters (FS, OS) have been specified

(often 5V)

p = pressure [bar]

FS = full-scale span [V]

OS = zero pressure offset [V]

[ppm/

C]

C]

[

C]

T = actual temperature to be measured [

C]

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