DA6505.005

11 June 2018

39 (44)

APPLICATION INFORMATION (continued)

Figure 15. Typical EEPROM read only application circuit in I2C bus communication

Together with a resistive pressure sensor, MAS6505

can be used in pressure measurement applications.

An

external

micro-controller

can

control

the

MAS6505 via an I2C or a SPI serial interface. Note

that the I2C serial interface requires suitable pull-up

resistors connected to the SDI and SCK pins (see

Figure 15). If there is only a single master device

connected to the serial bus the master’s SCK output

can be of push-pull type making the SCK pull-up

resistor unnecessary.

The sensor is connected between regulated Sensor

bridge supply voltage (VDDS) and Sensor bridge

supply ground (GNDS) of MAS6505. The sensor

output is read as a differential signal through PI

(positive input) and NI (negative input) to the ΔΣ

converter in MAS6505.

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 ma

rked “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.

A decoupling capacitor of at least 10

F should be

used at the supply voltage VDD for low noise

performance (see Figure 15).

In EEPROM read

only application (EEPROM

calibration memory readily programmed) the supply

voltage

operating range

is

VDD

=1.71V…5.5V.

However if both EEPROM write and read are needed

in application level the 5V supply voltage is

necessary

(VDD=4.5V…5.5V) as shown in Figure 4.

GND

SENSOR

VDD C

VDD

10µF

NOTE: In I2C bus communication the CSB pin is unused and left unconnected (floating). It has an internal pull up to VDDIO.

MCU

I/O

I/O

GND

GND

VDD

VDDIO

4.7k

4.7k

VDDIO

R2

R4

R1

R3

ADC

PI

NI

GNDS

VDDS

P

T

P

T

P

T

T

GND

VDD

CONTROL

VREFN

VREFP

OSC

EEPROM

SCK

MAS6505

SDO

CSB

VDDIO

TEST

MUX

SDO

VDDS

AFE

SDI

I2C/

SPI

GND

TD

REG

100nF

OPTIONAL TEMPERATURE

SENSING DIODE