DA6502.008
29 November 2012
APPLICATION INFORMATION
CVDD
4.7µ
VDD
VDD
VDD
GND
RP
4.7k
TE3
OSC
VDD
VDD
EEPROM
RP
4.7k
VREFP
ADC
PI
NI
P
T
SDA
SENSOR
I/O
I/O
I/O
I/O
CONTROL
I2C
P
T
SCL
XCLR
EOC
VDD
COMMON
R3
NOTE 1
VREFN
R1
OPTIONAL
R4
R2
TEST
MAS6502
T
P
T
MCU
TE1 TE2
GND
GND
GND
GND
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.
Figure 4. Typical application circuit
Together with a resistive pressure sensor,
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.
MAS6502 can be used in pressure measurement
applications. An external micro-controller can
control the MAS6502 via an I2C serial interface.
Note that the I2C serial interface requires suitable
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.
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
C
VDD in figure 4).
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.
13 (20)
MAS [ MICRO ANALOG SYSTEMS ]
