MS5540-CM

MS5540C (RoHS*) MINIATURE BAROMETER MODULE • 10 - 1100 mbar absolute pressure range • 6 coefficients for software compensation stored on-chip • Piezoresistive silicon micromachined sensor • Integrated miniature pressure sensor 6.2 x 6.4 mm • 16 Bit ADC • 3-wire serial interface • 1 system clock line (32.768 kHz) • Low voltage and low power consumption • RoHS-compatible & Pb-free* DESCRIPTION The MS5540C is a SMD-hybrid device including a precision piezoresistive pressure sensor and an ADCInterface IC. It is a miniature version of the MS5534C barometer/altimeter module and provides a 16 Bit data word from a pressure and temperature dependent voltage. MS5540C is a low power, low voltage device with automatic power down (ON/OFF) switching. A 3-wire interface is used for all communications with a microcontroller. Compared to MS5534A the pressure range (measurement down to 10 mbar) has been improved. The MS5540C is fully software compatible to the MS5534C and previous versions of MS5540. In addition, the MS5540C is from its outer dimensions compatible to the MS54XX series of pressure sensors. Compared to the previous version the ESD sensitivity level has been improved to 4kV on all pins. The gel protection of the sensor provides a water protection sufficient for 100 m waterproof watches without any additional protection. FEATURES • • • • • • Resolution 0.1 mbar Supply voltage 2.2 V to 3.6 V Low supply current < 5 µA Standby current < 0.1 µA -40° to +85° operation temperature C C No external components required APPLICATIONS • • • • Mobile altimeter/barometer systems W eather control systems Adventure or multi-mode watches GPS receivers BLOCK DIAGRAM VDD MCLK Input MUX SENSOR +IN dig. Filter Digital Interface ADC DIN DOUT SCLK -IN Sensor Interface IC SGND Memory (PROM) 64 bits GND Fig. 1: Block diagram MS5540C. * The European RoHS directive 2002/95/EC (Restriction of the use of certain Hazardous Substances in electrical and electronic equipment) bans the use of lead, mercury, cadmium, hexavalent chromium and polybrominated biphenyls (PBB) or polybrominated diphenyl ethers (PBDE). DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 1 PIN CONFIGURATION Fig. 2: Pin configuration of MS5540C. Pin Name SCLK GND PV (1) PEN (1) VDD MCLK DIN DOUT Pin 1 2 3 4 5 6 7 8 Type I G N I P I I O Function Serial data clock Ground Negative programming voltage Programming enable Positive supply voltage Master clock (32.768 kHz) Serial data input Serial data output NOTE 1) Pin 3 (PV) and PIN 4 (PEN) are only used by the manufacturer for calibration purposes and should not be connected. ABSOLUTE MAXIMUM RATINGS Parameter Supply voltage Storage temperature Overpressure Symbol VDD TS P Conditions Ta = 25 C Ta = 25 oC o Min -0.3 -40 Max 4 +85 10 Unit V C bar o Notes 1 2 NOTES 1) Storage and operation in an environment of dry and non-corrosive gases. 2) The MS5540C is qualified referring to the ISO Standard 2281 and can withstand an absolute pressure of 11 bar in salt water or 100 m water respectively. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 2 RECOMMENDED OPERATING CONDITIONS (Ta = 25° VDD = 3.0 V unless noted otherwise) C, Parameter Operating pressure range Supply voltage Supply current, average (1) during conversion (2) standby (no conversion) Current consumption into MCLK (3) Operating temperature range Conversion time External clock signal (4) Duty cycle of MCLK Serial data clock Symbol p VDD Conditions Min. 10 2.2 Typ. Max 1100 Unit mbar abs. V µA mA µA µA ° C ms kHz % kHz 3.0 4 1 3.6 VDD = 3.0 V Iavg Isc Iss MCLK = 32.768 kHz T tconv MCLK SCLK MCLK = 32.768 kHz 30.000 40/60 32.768 50/50 -40 +25 0.1 0.5 +85 35 35.000 60/40 500 NOTES 1) Under the assumption of one conversion every second. Conversion means either a pressure or a temperature measurement started by a command to the serial interface of MS5540C. 2) During conversion the sensor will be switched on and off in order to reduce power consumption; the total on time within a conversion is about 2 ms. 3) This value can be reduced by switching off MCLK while MS5540C is in standby mode. 4) It is strongly recommended that a crystal oscillator be used because the device is sensitive to clock jitter. A square-wave form of the clock signal is a must. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 3 ELECTRICAL CHARACTERISTICS DIGITAL INPUTS (T = -40° .. 85° VDD = 2.2 V .. 3.6 V) C C, Parameter Input High Voltage Input Low Voltage Signal Rise Time Signal Fall Time Symbol VIH VIL tr tf Conditions Min 80% VDD 0% VDD Typ Max 100% VDD 20% VDD Unit V V ns ns 200 200 DIGITAL OUTPUTS (T = -40° .. 85° VDD = 2.2 V .. 3.6 V) C C, Parameter Output High Voltage Output Low Voltage Signal Rise Time Signal Fall Time AD-CONVERTER Symbol VOH VOL tr tf Conditions Isource = 0.6 mA Isink = 0.6 mA Min 80% VDD 0% VDD Typ Max 100% VDD 20% VDD Unit V V ns ns 200 200 (T = -40° .. 85° VDD = 2.2 V .. 3.6 V) C C, Parameter Resolution Linear Range Conversion Time INL Symbol Conditions Min Typ 16 Max Unit Bit 4000 MCLK = 32.768 kHz Within linear range 40000 35 LSB ms LSB -5 +5 DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 4 PRESSURE OUTPUT CHARACTERISTICS W ith the calibration data stored in the interface IC of the MS5540C the following characteristics can be achieved: (VDD = 3.0 V unless noted otherwise) Typ Max Unit Notes 0.1 p = 750 .. 1100 mbar Ta = 25° C p = 750 .. 1100 mbar Ta = 25° C T = 0 .. +50° C p = 300 .. 1000 mbar T = -40 .. +85° C p = 300 .. 1000 mbar 12 months VDD = 2.2 .. 3.6 V p = const. -1.5 -0.5 -1 -2 -1 -1.6 +1.6 +1.5 +0.5 +1 +5 mbar mbar mbar mbar mbar mbar mbar 1 2 3 4 4 5 Parameter Resolution Absolute Pressure Accuracy Relative Pressure Accuracy Relative Pressure Error over Temperature Long-term Stability Maximum Error over Supply Voltage Conditions Min NOTES 1) A stable pressure reading of the given resolution requires taking the average of 2 to 4 subsequent pressure values due to noise of the ADC. 2) Maximum error of pressure reading over the pressure range. 3) Maximum error of pressure reading over the pressure range after offset adjustment at one pressure point. 4) With the second-order temperature compensation as described in Section “FUNCTION". See next section for typical operating curves. 5) The long-term stability is measured with non-soldered devices. TEMPERATURE OUTPUT CHARACTERISTICS This temperature information is not required for most applications, but it is necessary to allow for temperature compensation of the pressure output. (VDD = 3.0 V unless noted otherwise) Parameter Conditions Min Typ Max Unit Notes Resolution Accuracy Maximum Error over Supply Voltage T = 20° C T = -40 .. +85° C VDD = 2.2 .. 3.6 V 0.005 -0.8 -2 -0.2 0.01 0.015 0.8 +3 + 0.2 ° C ° C ° C ° C 1 2 NOTES 1) With the second-order temperature compensation as described in Section “FUNCTION". See next section for typical operating curves. 2) At Ta = 25 ° C DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 5 TYPICAL PERFORMANCE CURVES ADC-value D1 vs Pressure (typical) 22000 20000 18000 ADC-value D1 (LSB) 16000 14000 -40°C 25° C 85° C 12000 10000 8000 6000 0 100 200 300 400 500 600 700 800 900 1000 1100 Pressure (mbar) ADC-value D2 vs Temperature (typical) 40000 35000 ADC-value D2 (LSB) 30000 25000 20000 15000 -40 -20 0 20 Temperature (° C) 40 60 80 Absolute Pressure Accuracy after Calibration, 2nd order compensation 4 3 2 Pressure error (mbar) 1 85° C 60° C 0 25° C 0° C -40° C -1 -2 -3 -4 0 100 200 300 400 500 600 700 800 900 1000 1100 Pressure (mbar) DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 6 Temperature Error Accuracy vs temperature (typical) 15 10 Temperature error (° C) Temperature error (standard calculation) 5 Temperature error (with 2nd order calculation) 0 -5 -40 -20 0 20 Temperature (° C) 40 60 80 Pressure Error Accuracy vs temperature (typical) 18 16 14 12 10 Pressure error (mbar) 8 6 4 2 0 -2 -4 -6 -8 -40 -20 0 20 Temperature (° C) 40 60 80 Perror(1000,1st order) Perror(1000,2nd order) Perror(800,1st order) Perror(800,2nd order) Perror(300,1st order) Perror(300,2nd order) DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 7 Pressure error vs supply voltage (typical) 1 0.8 0.6 0.4 Pressure error (mbar) 0.2 0 2.2 -0.2 2.4 2.6 2.8 3 3.2 3.4 3.6 1000mbar 800mbar 300mbar -0.4 -0.6 -0.8 -1 Voltage (V) Temperature error vs supply voltage (typical) 0.15 0.1 Temperature error (° C) 0.05 0 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 -0.05 -0.1 -0.15 Voltage (V) DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 8 FUNCTION GENERAL The MS5540C consists of a piezoresistive sensor and a sensor interface IC. The main function of the MS5540C is to convert the uncompensated analogue output voltage from the piezoresistive pressure sensor to a 16-Bit digital value, as well as providing a 16-Bit digital value for the temperature of the sensor. • measured pressure (16-Bit) • measured temperature (16-Bit) “D1” “D2” As the output voltage of a pressure sensor is strongly dependent on temperature and process tolerances, it is necessary to compensate for these effects. This compensation procedure must be performed by software using an external microcontroller. D1 D2 W ord1..4 Pressure Sensor Calculation in external microcontroller Temperature For both pressure and temperature measurement the same ADC is used (sigma delta converter): • for the pressure measurement, the differential output voltage from the pressure sensor is converted • for the temperature measurement, the sensor bridge resistor is sensed and converted During both measurements the sensor will only be switched on for a very short time in order to reduce power consumption. As both, the bridge bias and the reference voltage for the ADC are derived from VDD, the digital output data is independent of the supply voltage. FACTORY CALIBRATION Every module is individually factory calibrated at two temperatures and two pressures. As a result, 6 coefficients necessary to compensate for process variations and temperature variations are calculated and stored in the 64Bit PROM of each module. These 64-Bit (partitioned into four words of 16-Bit) must be read by the microcontroller software and used in the program converting D1 and D2 into compensated pressure and temperature values. PRESSURE AND TEMPERATURE MEASUREMENT The sequence of reading pressure and temperature as well as of performing the software compensation is depicted in Fig. 3 and Fig. 5. First the Word1 to Word4 have to be read through the serial interface. This can be done once after reset of the microcontroller that interfaces to the MS5540C. Next the compensation coefficients C1 to C6 are extracted using Bit-wise logical- and shift-operations (refer to Fig. 4 for the Bit-pattern of Word1 to Word4). For the pressure measurement the microcontroller has to read the 16 Bit values for pressure (D1) and temperature (D2) via the serial interface in a loop (for instance every second). Then, the compensated pressure is calculated out of D1, D2 and C1 to C6 according to the algorithm in Fig. 3 (possibly using quadratic temperature compensation according to Fig. 5). All calculations can be performed with signed 16-Bit variables. Results of multiplications may be up to 32-Bit long (+sign). In the flow according to Fig. 3 each multiplication is followed by a division. This division can be performed by Bit-wise shifting (divisors are to the power of 2). It is ensured that the results of these divisions are less than 65536 (16-Bit). For the timing of signals to read out Word1 to Word4, D1, and D2 please refer to the paragraph “Serial Interface”. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 9 Start System initialisation Read calibration data (factory calibrated) from PROM of MS5540 Word1, Word2, Word3 and Word4 (4x16 Bit) Basic equations: Example: Word1 = 46940 Word2 = 40217 Word3 = 25172 Word4 = 47212 Convert calibration data into coefficients: (see bit pattern of Word1-Word4) C1: Pressure sensitivity C2: Pressure offset C3: Temperature coefficient of pressure sensitivity C4: Temperature coefficient of pressure offset C5: Reference Temperature C6: Temperature coefficient of the temperature (15 Bit) (12 Bit) (10 Bit) (10 Bit) (11 Bit) (6 Bit) SENST1 OFFT1 TCS TCO Tref TEMPSENS C1 = 23470 C2 = 1324 C3 = 737 C4 = 393 C5 = 628 C6 = 25 Pressure and temperature measurement Read digital pressure value from MS5540 D1 (16 Bit) D1 = 16460 Read digital temperature value from MS5540 D2 (16 Bit) D2 = 27856 UT1 = 25248 Calculate calibration temperature UT1 = 8*C5+20224 Calculate actual temperature Difference between actual temperature and reference temperature: dT(D2) = D2 - Tref TEMP(D2) = 20°+dT(D2)*TEMPSENS dT = 2608 dT = D2 - UT1 Actual temperature: TEMP = 200 + dT*(C6+50)/2 (0.1°C resolution) 10 TEMP = 391 C = 39.1 ° Calculate temperature compensated pressure Offset at actual temperature: OFF(D2) = OFFT1+TCO*dT(D2) SENS(D2) = SENST1+TCS*dT(D2) OFF = C2*4 + ((C4-512)*dT)/212 Sensitivity at actual temperature: OFF = 5220 SENS = 49923 X = 23093 = 9716 = 971.6 mbar SENS = C1 + (C3*dT)/210 + 24576 X = (SENS * (D1-7168))/214 - OFF Temperature compensated pressure: P = X*10/25 + 250*10 (0.1 mbar resolution) P(D1,D2) = D1*SENS(D2)-OFF(D2) P Display pressure and temperature value Fig. 3: Flow chart for pressure and temperature reading and software compensation. NOTES 1) Readings of D2 can be done less frequently, but the display will be less stable in this case. 2) For a stable display of 0.1 mbar resolution, it is recommended to display the average of 8 subsequent pressure values. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 10 C1 (15 Bit) C5/I 1 Bit W ord1 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB10 C5/II (10 Bit) W ord2 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB5 DB4 C6 (6 Bit) DB3 DB2 DB1 DB0 C4 (10 Bit) W ord3 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB11 DB10 C2/I (6 Bit) DB9 DB8 DB7 DB6 C3 (10 Bit) W ord4 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB5 DB4 C2/II (6-Bit) DB3 DB2 DB1 DB0 Fig. 4: Arrangement (Bit-pattern) of calibration data in Word1 to Word4. SECOND-ORDER TEMPERATURE COMPENSATION In order to obtain best accuracy over the whole temperature range, it is recommended to compensate for the non-linearity of the output of the temperature sensor. This can be achieved by correcting the calculated temperature and pressure by a second order correction factor. The second-order factors are calculated as follows: TEMP < 200 200 ≤ TEMP ≤ 450 TEMP > 450 yes yes yes Low Temperatures T2 = 11*(C6+24)*(200 - TEMP)*(200 – TEMP) / 220 P2 = 3 *T2 * (P - 3500)/2 14 No correction T2 = 0 P2 = 0 High Temperatures T2 = 3*(C6+24)*(450 - TEMP)*(450 – TEMP) / 220 P2 = T2 * (P - 10000)/213 Calculate pressure and temperature TEMP = TEMP – T2 P = P – P2 Fig. 5: Flow chart for calculating the temperature and pressure to the optimum accuracy. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 11 SERIAL INTERFACE The MS5540C communicates with microprocessors and other digital systems via a 3-wire synchronous serial interface as shown in Fig. 1. The SCLK (Serial clock) signal initiates the communication and synchronises the data transfer with each Bit being sampled by the MS5540C on the rising edge of SCLK and each Bit being sent by the MS5540C on the rising edge of SCLK. The data should thus be sampled by the microcontroller on the falling edge of SCLK and sent to the MS5540C with the falling edge of SCLK. The SCLK-signal is generated by the microprocessor’s system. The digital data provided by the MS5540C on the DOUT pin is either the conversion result or the software calibration data. In addition the signal DOUT (Data out) is also used to indicate the conversion status (conversion-ready signal, see below). The selection of the output data is done by sending the corresponding instruction on the pin DIN (Data input). Following is a list of possible output data instructions: • • • • • • • Conversion start for pressure measurement and ADC-data-out Conversion start for temperature measurement and ADC-data-out Calibration data read-out sequence for Word1 Calibration data read-out sequence for Word2 Calibration data read-out sequence for Word3 Calibration data read-out sequence for Word4 RESET sequence “D1” “D2” (Figure 6a) (Figure 6b) (Figure 6c) (Figure 6d) (Figure 6c) (Figure 6d) (Figure 6e) Every communication starts with an instruction sequence at pin DIN. Fig. 6 shows the timing diagrams for the MS5540C. The device does not need a ‘Chip select’ signal. Instead there is a START sequence (3-Bit high) before each SETUP sequence and STOP sequence (3-Bit low) after each SETUP sequence. The SETUP sequence consists in 4-Bit that select a reading of pressure, temperature or calibration data. In case of pressure(D1) or temperature- (D2) reading the module acknowledges the start of a conversion by a low to high transition at pin DOUT. Two additional clocks at SCLK are required after the acknowledge signal. Then SCLK is to be held low by the microcontroller until a high to low transition on DOUT indicates the end of the conversion. This signal can be used to create an interrupt in the microcontroller. The microcontroller may now read out the 16-Bit word by giving another 17 clocks on the SLCK pin. It is possible to interrupt the data READOUT sequence with a hold of the SCLK signal. It is important to always read out the last conversion result before starting a new conversion. The RESET sequence is special as its unique pattern is recognised by the module in any state. By consequence it can be used to restart if synchronisation between the microcontroller and the MS5540C has been lost. This sequence is 21-Bit long. The DOUT signal might change during that sequence (see Fig. 6e). It is recommended to send the RESET sequence before first CONVERSION sequence to avoid hanging up the protocol permanently in case of electrical interference. DOUT SCLK Conversion start for pressure measurement and ADC-data-out "D1": end of conversion start of conversion conversion (33ms) ADC-data out M SB DB7 DB6 DB5 DB4 DB3 DB2 DB1 ADC-data out LSB DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DIN sequence: START+P-measurement Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Start-bit Setup-bits Stop-bit Fig. 6a: D1 ACQUISITION sequence. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 12 DOUT SCLK Conversion start for temperature measurement and ADC-data-out "D2": end of conversion start of conversion conversion (33ms) ADC-data out M SB DB7 DB6 DB5 DB4 DB3 DB2 DB1 ADC-data out LSB DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DIN sequence: START+T-measurement Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Start-bit Setup-bits Stop-bit Fig. 6b: D2 ACQUISITION sequence. DOUT SCLK Calibration data read out sequence for word 1/ word 3: coefficient-data out M SB DB7 DB6 DB5 DB4 DB3 DB2 DB1 sequence: coefficient read + address Bit0 Bit1 Bit2 Start-bit Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Setup-bits Stop-bit address word 1 coefficient-data out LSB DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DIN address word 3 Fig. 6c: Word1, Word3 READING sequence. DOUT SCLK Calibration data read out sequence for word 2/ word 4: coefficient-data out M SB DB7 DB6 DB5 DB4 DB3 DB2 DB1 sequence: coefficient read + address Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Start-bit Setup-bits Stop-bit address word 2 coefficient-data out LSB DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DIN address word 4 Fig. 6d: W2, W4 READING sequence. DIN DOUT SCLK RESET - sequence: sequence: RESET Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11Bit12 Bit13 Bit14 Bit15 Fig. 6e: RESET sequence (21-Bit). DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 13 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 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 software allows the user to adapt it to his particular application. Communication between the MS5540C 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 Bitmicrocontroller applications. CALIBRATION The MS5540C 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 an anticorrosive and antimagnetic protection cap. The MS5540C 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 MS5540C 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 Oring 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 MS5540C 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 MS5540C's ceramic substrate with glue or Globtop-like material. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 14 DECOUPLING CAPACITOR Particular care must be taken when connecting the device to power supply. A 47 µF tantalum capacitor must be placed as close as possible of the MS5540C's VDD pin. This capacitor will stabilise the power supply during data conversion and thus, provide the highest possible accuracy. APPLICATION EXAMPLE: ALTIMETER SYSTEM USING MS5540C MS5540C is a circuit that can be used in connection with a microcontroller in mobile altimeter applications. It is designed for low-voltage systems with a supply voltage of 3 V, particularly in battery applications. The MS5540C is optimised for low current consumption as the AD-converter clock (MCLK) can use the 32.768 kHz frequency of a standard watch crystal, which is supplied in most portable watch systems. For applications in altimeter systems Intersema can deliver a simple formula to calculate the altitude, based on a linear interpolation, where the number of interpolation points influences the accuracy of the formula. 3V-Battery LCD-Display VDD XTAL1 32.768 kHz MS5540C VDD MCLK DIN DOUT SCLK GND GND 47µF Tantal XTAL2 Keypad 4/8bit-Microcontroller EEPROM optional Figure 7: Demonstration of MS5540C in a mobile altimeter. RECOMMENDED PAD LAYOUT Pad layout for bottom side of MS5540C soldered onto printed circuit board DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 15 DEVICE PACKAGE OUTLINES Fig. 8: Device package outlines of MS5540C. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 16 ASSEMBLY MECHANICAL STRESS It is recommended to avoid mechanical stress on the PCB on which the sensor is mounted. The thickness of the PCB should not be below 1.6 mm. A thicker PCB is stiffer creating less stress on the soldering contacts. For applications where mechanical stress cannot be avoided (for example ultrasound welding of the case or thin PCB’s in watches) please fix the sensor with drops of low stress epoxy (for example Hysol FP-4401). MOUNTING The MS5540C can be placed with automatic Pick&Place equipment using vacuum nozzles. It will not be damaged by the vacuum. Due to the low stress assembly the sensor does not show pressure hysteresis effects. Special care has to be taken to not touch the protective gel of the sensor during the assembly. It is important to solder all contact pads. The Pins PEN and PV shall be left open or connected to VDD. Do not connect the Pins PEN and PV to GND! SEALING WITH O-RING In products like outdoor watches the electronics must be protected against direct water or humidity. For those products the MS5540C provides the possibility to seal with an O-ring. The protective cap of the MS5540C is made of special anticorrosive and antimagnetic stainless steel with a polished surface. In addition to this the MS5540C is filled with silicone gel covering the sensor and the bonding wires. The O-ring (or O-rings) shall be placed at the outer diameter of the metal cap. This method avoids mechanical stress because the sensor can move in vertical direction. CLEANING The MS5540C has been manufactured under cleanroom conditions. Each device has been inspected for the homogeneity and the cleanness of the silicone gel. It is therefore recommended to assemble the sensor under class 10’000 or better conditions. Should this not be possible, it is recommended to protect the sensor opening during assembly from entering particles and dust. To avoid cleaning of the PCB, solder paste of type “no-clean” shall be used. Cleaning might damage the sensor! ESD PRECAUTIONS The electrical contact pads are protected against ESD up to 4 kV HBM (human body model). It is therefore essential to ground machines and personal properly during assembly and handling of the device. The MS5540C is shipped in antistatic transport boxes. Any test adapters or production transport boxes used during the assembly of the sensor shall be of an equivalent antistatic material. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 17 ORDERING INFORMATION Product Code Product Miniature Barometer Module with metal cap Art.-Nr. Package SMD hybrid with solder paste, anticorrosive and antimagnetic metal protection cap, silicon gel sensor protection Comments Recommended for outdoor products MS5540-CM 325540009 FACTORY CONTACTS Intersema Sensoric SA Ch. Chapons-des-Prés 11 CH-2022 BEVAIX SWITZERLAND Tel. 032 847 9550 Tel. Int. +41 32 847 9550 Telefax +41 32 847 9569 e-mail: http://www.intersema.ch NOTICE Intersema reserves the right to make changes to the products contained in this data sheet in order to improve the design or performance and to supply the best possible products. Intersema assumes no responsibility for the use of any circuits shown in this data sheet, conveys no license under any patent or other rights unless otherwise specified in this data sheet, and makes no claim that the circuits are free from patent infringement. Applications for any devices shown in this data sheet are for illustration only and Intersema makes no claim or warranty that such applications will be suitable for the use specified without further testing or modification. DA5540C_003 0005540C1193 ECN 1118 June 16th, 2008 18