DA6502.008

29 November 2012

13 (20)

APPLICATION INFORMATION

Figure 4. Typical application circuit

Together

with

a

resistive

pressure

sensor,

MAS6502 can be used in pressure measurement

applications.

An

external

micro-controller

can

control the MAS6502 via an I

Note that the I

pull up resistors connected to the SDA and SCL

pins (see figure 4). Note that if there is only a single

master device in the serial bus the master’s SCL

output can be push-pull output stage making the

SCL pull-up resistor unnecessary.

The sensor is connected between the power supply

voltage

(VDD)

and

MAS6502

signal

ground

(COMMON) which can be internally connected to

ground (GND). The sensor output is read as a

differential signal through PI (positive input) and NI

(negative input) to the Σ converter in MAS6502.

In the pressure measurement mode, the switches

marked “P” are closed and the sensor output is fed

through

to

the

ADC.

In

the

temperature

measurement mode, the switches marked “T” are

closed and the voltage at the ADC input is

determined by the internal resistor array and the

temperature-dependent resistance of the sensor. In

this configuration the sensor bridge is connected as

part of a Wheatstone resistor bridge circuit where

the other four resistors (R1, R2, R3, R4) are inside

the IC.

To guarantee conversion accuracy a supply voltage

decoupling capacitor of 4.7 µF or more should be

placed between VDD and GND of MAS6502 (see

Accuracy Improvement – Averaging

An averaging technique can be used to remove

conversion error caused by noise and thus improve

measurement accuracy. By doing several A/D

conversions and calculating the average result it’s

possible to average out noise. Theoretically random

noise is reduced by a factor

N

where N is the

number

of

averaged

samples.

A/D

converter

nonlinearities cannot be removed by averaging.

GND

R2

R4

R1

R3

ADC

PI

NI

COMMON

VDD

P

T

P

T

P

T

T

GND

VDD

CONTROL

SENSOR

VREFN

VREFP

TEST

I

OSC

EEPROM

SDA

SCL

TE3

EOC

XCLR

TE1

TE2

MAS6502

MCU

OPTIONAL

VDD

GND

I/O

I/O

I/O

I/O

GND

GND

VDD

VDD

4.7k

4.7k

4.7µ

µ

µ

µ

VDD

NOTE 1. It is recommended to use the XCLR reset feature to solve

unexpected error state conditions. The XCLR pin can be left

unconnected if not used. It has internal pull up to VDD.

NOTE 1