DA6502.008
29 November 2012
OPERATING MODES
MAS6502 has two operating modes, pressure and
temperature measurement mode. In the pressure
mode the pressure dependent sensor bridge
voltage is connected to the ADC input. In the
temperature measurement mode the resistive
sensor is connected into a Wheatstone resistor
bridge circuit together with four internal resistors
(see Temperature Measurement Configuration in
the Application Information chapter) and the
temperature dependent bridge output voltage is
connected to the ADC input.
Switching between pressure and temperature
measurement modes is done via the single ADC
control register. The measurement configuration
includes selection of over sampling ratio, input
signal range, offset and sensor resistance. By
writing an 8-bit configuration data to the ADC
control register a new A/D conversion is started.
See further details in the ADC Control Register
chapter.
MAS6502 includes a 256-bit EEPROM memory for
storing trimming and calibration data on chip. The
first 8-bits of EEPROM are reserved for internal
oscillator trimming but the remaining 248-bits are
free for calibration and other data.
The stored calibration data should comprise of
calibration
and
temperature
compensation
coefficients which can be used to calculate accurate
calibrated pressure and temperature measurement
results from the non-calibrated measurement
results. All calculations need to be done in the
external micro controller unit (MCU).
A calibrated MAS6502 sensor system is operated
as illustrated in figure 2. The calibration and
compensation coefficients need to be read to the
MCU memory only once. From each pair of
pressure and temperature measurements results
the accurate pressure and temperature values are
then calculated by using the external MCU.
All communication with MAS6502 is done using the
2
bi-directional I C
®
bus compatible 2-wire serial bus.
Starting an A/D conversion, reading out the
conversion result and reading and writing data from
and to the EEPROM memory are all accomplished
via serial bus communication.
2
In addition to the I C
®
bus the digital interface
includes also end-of-conversion (EOC) and master
reset (XCLR) pins. See A/D Conversion in the Serial
2
Data Interface (I C
®
Bus) Control chapter.
START
READ EEPROM
CALIBRATION DATA
MEASURE PRESSURE
MEASURE TEMPERATURE
CALCULATE CALIBRATED
TEMPERATURE
CALCULATE TEMPERATURE
COMPENSATED PRESSURE
Figure 2.
Flow chart for a calibrated MAS6502 sensor system
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MAS [ MICRO ANALOG SYSTEMS ]
