MLX90314_12 Datasheet, PDF (9/28 Pages) Melexis Microelectronic Systems – Programmable Sensor Interface

MLX90314
Programmable Sensor Interface
Analog Features Power-On Reset
The Power-On Reset (POR) initializes the state of the
Supply Regulator
digital part after power up. The reset circuitry is
completely internal. The chip is completely reset and
A bandgap-stabilized supply-regulator is on-chip while _{fully operational 3.5 ms from the time the supply crosses}
the pass-transistor is external. The bridge-type sensor _{3.5 volts. The POR circuitry will issue another POR if}
is typically powered by the regulated supply (typically _{the supply voltage goes below this threshold for 1.0 us.}
4.75V). For ratiometric operation, the supply-regulator
can be disabled by connecting
unregulated and regulated supply pins.
together
the _{Test Mode}
For 100% testability, a "TEST" pin is provided. If the pin
Oscillator
is pulled low, then the monitor program is entered and
the chip changes its functionality. In all other
The MLX90314 contains a programmable on-chip RC _{applications, this pin should be pulled high or left}
oscillator. No external components are needed to set _{floating (internal pull-up).}
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 frequency of the internal clock is stabilized over _{the external or internal temperature sensor. This is}
the full temperature range, which is divided into three _{converted to a 10-bit number for use in calculating the}
regions, each region having a separate digital clock _{signal compensation factors. A 2-bit coarse adjustment}
setting. All of the clock frequency programming is _{GNTP[1:0] is used for the temperature signal gain &}
done by Melexis during final test of the component. offset adjustment.
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 a
capacitor.
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.
3901090314
Rev 008
Page 9
Apr/12