DA6512.003
2 December, 2016
OPERATING MODES
MAS6512 has two capacitance measurement
modes, a temperature measurement mode and a
VDD level monitoring mode. In capacitance
measurement mode the output is proportional to
either capacitance difference (CS-CR) or to
capacitance ratio (CS-CR)/CS. In temperature
measurement mode the output is proportional to the
absolute temperature. The VDD level monitoring
mode allows measuring supply voltage which can
be useful especially in battery operated systems.
The stored calibration data should comprise of
calibration
and
temperature
compensation
coefficients that can be used to calculate accurate
sensor and temperature measurement results from
the non-calibrated measurement readings. All
calculations need to be done in an external micro
controller unit (MCU) which controls the MAS6512.
A calibrated MAS6512 sensor system should be
operated as illustrated in figure 2. Connecting VDD
triggers power-on-reset (POR) but to make sure the
device is reset an additional reset should be given
using the XCLR pin or writing any data on the reset
register E0/60HEX via the serial bus.
Measurement mode configuration and start of
conversion is done by writing 8-bit configuration
data to the Measurement control register (address
E2HEX). See further details in the Measurement
control register chapter.
The calibration and compensation coefficients are
necessary to be read to the MCU memory only
once. From each pair of sensor and temperature
measurement readings and using the calibration
coefficients the accurate sensor and temperature
values can then be calculated in the external MCU.
MAS6512 includes a 256-bit EEPROM memory for
storing trim and calibration data on chip. Five bytes
(40 bits) of EEPROM are reserved for trim values
and programmable I2C device address but the
remaining 27 bytes (216 bits) are free for storing
sensor calibration and other data.
All communication with MAS6512 is done using
either the I2C bus or the SPI bus. Starting an A/D
conversion, reading the conversion result and
reading and writing data from and to the EEPROM
memory are all accomplished via serial bus
communication.
The stored trim data consists of capacitive front-end
offset and gain setting data that are automatically
read from EEPROM memory in the beginning of
each conversion (in normal operating mode). The
programmable I2C device address is read from
EEPROM memory only during power on reset or by
manual reset using XCLR or the reset register.
In addition to the serial buses the digital interface
includes also end-of-conversion (EOC) and master
reset (XCLR) pins. See A/D Conversion in the Serial
Data Interface (I2C Bus) Control chapter.
POWER UP / RESET
Reset device by XCLR or
by writing any data to the reset register E0/60HEX
READ EEPROM
CALIBRATION DATA
MEASURE SENSOR
MEASURE TEMPERATURE
CALCULATE CALIBRATED
TEMPERATURE
CALCULATE TEMPERATURE
COMPENSATED SENSOR VALUE
Figure 2. Flow chart for a calibrated MAS6512 sensor system
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MAS [ MICRO ANALOG SYSTEMS ]
