MLX90314
Programmable Sensor Interface
Analog Features
Supply Regulator
A bandgap-stabilized supply-regulator is on-chip while
the pass-transistor is external. The bridge-type sensor
is typically powered by the regulated supply (typically
4.75V). For ratiometric operation, the supply-regulator
can be disabled by connecting together the
unregulated and regulated supply pins.
Power-On Reset
The Power-On Reset (POR) initializes the state of the
digital part after power up. The reset circuitry is
completely internal. The chip is completely reset and
fully operational 3.5 ms from the time the supply crosses
3.5 volts. The POR circuitry will issue another POR if
the supply voltage goes below this threshold for 1.0 us.
Test Mode
For 100% testability, a "TEST" pin is provided. If the pin
is pulled low, then the monitor program is entered and
the chip changes its functionality. In all other
applications, this pin should be pulled high or left
floating (internal pull-up).
Oscillator
The MLX90314 contains a programmable on-chip RC
oscillator. No external components are needed to set
the frequency (87.8 kHz +/-1%). The MCU-clock is
generated by a PLL (phase locked loop tuned for 614
kHz or 2.46 Mhz) which locks on the basic oscillator.
Temperature Sense
The temperature measurement, TPO, is generated from
the external or internal temperature sensor. This is
converted to a 10-bit number for use in calculating the
signal compensation factors. A 2-bit coarse adjustment
GNTP[1:0] is used for the temperature signal gain &
offset adjustment.
The frequency of the internal clock is stabilized over
the full temperature range, which is divided into three
regions, each region having a separate digital clock
setting. All of the clock frequency programming is
done by Melexis during final test of the component.
The device uses the internal temperature sensor to
determine which temperature range setting to use.
A/D and D/A
Conversions using only one DAC
For saving chip area, the "Offset DAC" is multiplexed
in various ways. Both "fine offset" and "digital mode"
signals are stored on a capacitor. An ADC-loop is
available by using a comparator and SAR.
D/A
Before changing to another capacitor, the DAC output
should be settled to the new value. For example,
MODSEL moves the analog multiplexer to the so-
called "open state 0." At the same time, the 10 bit mux
selects OF[9:0] for the offset-DAC. After the DAC
settling time, the analog multiplexer is moved to its
final state and the DAC-output is stored on
capacitor.
a
A/D
The S/W-Signal MODSEL connects the SAR-output to
the DAC and the DAC-output to the comparator. The
SARegister is initialized by a rising edge of STC (S/W
signal). At the end of the A/D conversion, the
EOC flag is set to 1 and the controller can read the
ADC values.
MLX902xx Name of Sensor Rev Y.X 22/Aug/98
3901090314
Page 9
Page 9
Nov/04
Rev 007
MELEXIS [ Melexis Microelectronic Systems ]
