MLX90807 Просмотр технического описания (PDF) - Melexis Microelectronic Systems

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MLX90807

Integrated Relative and Absolute Pressure Sensors

Melexis Microelectronic Systems  

MLX90807/90808

Integrated Relative and Absolute Pressure Sensors

5. General Description

This chip integrates a pressure sensor and the associated signal conditioning on the same die. The supply

voltage VDD directly supplies the pressure sensor.

The pressure sensing element consists of a square diaphragm realized in the silicon chip by backside

etching. Due to its small thickness this diaphragm reacts to a pressure difference at both of its side by

cambering. The internal strain increases, in particular at the border of the diaphragm. Here, the piezo-

resistive elements have been implanted into the silicon diaphragm, which act as transducer.

Four resistors are placed in a Wheatstone-bridge configuration at the four borders of the square diaphragm.

A chopped instrumentation stage amplifies the differential output signal of the sensor. The gain of this

amplifier can be adjusted with 3 bits. After the input stage, there is a 3 bit programmable coarse offset which

is followed by a differential to single-ended conversion. The reference voltage for this stage is generated by a

10 bit DAC and varies linearly with temperature in order to perform the offset and offset drift compensation. A

digital hardware multiplier calculates this compensation. The temperature signal, serving as input for this

multiplier, is generated from the ADC of the output signal of the internal temperature sensor.

The chopped signal is demodulated with a switched capacitor stage. The buffered output serves as reference

for a 10 bit DAC to perform the span and span drift compensation. The DAC is controlled by the digital part.

Finally the signal is given out by a class AB rail-to-rail amplifier capable of sourcing and sinking large

currents.

A calibration of the transfer function using 3 temperature points and 2-point pressure points per temperature

can be performed to achieve an error less than ±1% over the complete pressure and temperature range (the

output error is referred to the output span).

PTC (Programming Through Connector) protocol is used to perform calibration.

The programming of the sensor chip is carried out via the analog connections (i.e. supply, ground, signal out).

No additional pins are necessary for calibration. Melexis delivers all required hardware and software to

perform the calibration of the MLX90807 and MLX90808.

For more information on how to perform the calibration of the MLX90807/90808 consult the following

documents:

AN PTC 90807

Multi Sensor Calibration Board

AN Advanced Calibration 90807 90808

Software User Manual MLX90807 PTC04

6. Application Information

Only 3 pins are used in the application (Vdd, Vss, Out).

Calibration and Programming is made through the application pins.

Only a capacitor on the supply and output lines are necessary.

Rev 003

3901090808

Page 6 of 7

Data Sheet

Feb/12

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