APPLICATION INFORMATION
GENERAL
The advantage of combining a pressure sensor with a directly adapted integrated circuit is to save other external
components and to achieve a very low power consumption. The main application field for this system includes
portable devices with battery supply, but its high accuracy and resolution make it also suited for industrial and
automotive applications. The possibility to compensate the sensor with a software allows the user to adapt it to
his particular application. Communication between the MS5540B and the widely available microcontrollers is
realised over an easy-to-use 3-wire serial interface. Customers may select which microcontroller system to be
used, and there are no specific standard interface cells required, which may be of interest for specially designed
4 Bit-microcontroller applications.
CALIBRATION
The MS5540B is factory calibrated. The calibration data is stored inside the 64-Bit PROM memory.
SOLDERING
Please refer to the application note AN808 for all soldering issues.
HUMIDITY, WATER PROTECTION
The silicon pressure transducer and the bonding wires are protected by a anticorrosive and antimagnetic
protection cap. The MS5540B carries a metal protection cap filled with silicone gel for enhanced protection
against humidity. The properties of this gel ensure function of the sensor even when in direct water contact. This
feature can be useful for waterproof watches or other applications, where direct water contact cannot be
avoided. Nevertheless the user should avoid drying of hard materials like for example salt particles on the
silicone gel surface. In this case it is better to rinse with clean water afterwards. Special care has to be taken to
not mechanically damage the gel. Damaged gel could lead to air entrapment and consequently to unstable
sensor signal, especially if the damage is close to the sensor surface.
The metal protection cap is fabricated of special anticorrosive and antimagnetic stainless steel in order to avoid
any corrosive battery effects inside the final product. The MS5540B is qualified referring to the ISO Standard
2281 and can withstand a pressure of 11 bar in salt water. The concentration of the see water used for the
qualification is 41 g of see salt for 1 litre of DI water.
For underwater operations as specified in ISO Standard 2281 it is important to seal the sensor with a rubber O-
ring around the metal cap. Any salt water coming to the contact side (ceramic and pads) of the sensor could lead
to permanent damage. Especially for "water-resistant 100 m" watches it is recommended to provide a stable
mechanical pusher from the backside of the sensor. Otherwise the overpressure might push the sensor
backwards and even bend the electronic board on which the sensor is mounted.
LIGHT SENSITIVITY
The MS5540B is protected against sunlight by a layer of white gel. It is, however, important to note that the
sensor may still be slightly sensitive to sunlight, especially to infrared light sources. This is due to the strong
photo effect of silicon. As the effect is reversible there will be no damage, but the user has to take care that in
the final product the sensor cannot be exposed to direct light during operation. This can be achieved for instance
by placing mechanical parts with holes in such that light cannot pass.
CONNECTION TO PCB
The package outline of the module allows the use of a flexible PCB to connect it. This can be important for
applications in watches and other special devices, and will also reduce mechanical stress on the device.
For applications subjected to mechanical shock, it is recommended to enhance the mechanical reliability of the
solder junctions by covering the rim or the corners of MS5540B's ceramic substrate with glue or Globtop-like
material.
DA5540B_007
September 25th, 2006
14
00005540767 ECN 865
INTERSEMA [ INTERSEMA SENSORIC SA ]
