MS5541C Miniature 14 bar Module
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• 0 – 14 bar absolute pressure range
• 6 coeffi cients 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 consu m p tion
• High Endurance (HM version)
DESCRIPTION
The MS5541C is the miniature version of MS5535C pressure sensor module. The MS5541-HM is the high
endurance pad technology version of MS5541C pressure sensor module. It contains a precision piezoresistive
pressure sensor and an improved version of the 16 Bit Micropower Sensor interface IC known from the
MS5535C. Compared to the previous version the ESD sensitivity has been improved to 4kV on all pins. In
addition to t his the MS554 1C is f rom its outer dim ensions com patible to th e MS54 xx s eries of pressure s ensors .
It uses an antim agnetic po lis hed stainles s steel ring f or sealin g with O-r ing. T he sensor pr ovides 16 Bit pr essur e
and temperature data via a 3 wire serial interface that can be easily interfaced with 4 Bit low power
microcontrollers. 64 Bit of factory programmed PROM provides calibration data for a highly accurate pressure
and temper ature calculatio n. The MS5541C is fully software com patible to the M S5535C and previous versions
of MS5541.
FEATURES
FIELD OF APPL ICATION TECHNICAL DATA
•
Diving computers and watches
Sensor Performances (VDD = 3 V)
• Mobile water depth and measurement systems
• High endurance pad technology (HM version)
Pressure Min Typ Max Unit
Range 0 14 bar
FUNCTIONA L BLOCK DIAGRAM
VDD
GND
MCLK
SCLK
DOUT
DIN
Input MUX
ADC
Digital
Interface
Memory
(PROM)
64 bits
SENSOR
SGND
+IN
-IN
dig.
Filter
Sensor
Interface IC
ADC 16 bit
Resolution 1.2 mbar
Accuracy 0°C to +40°C,
0 to 10 bar
-50 +20 mbar
Accuracy -40°C to
+85°C
0 to 10 bar
-60 +180 mbar
Response time 35 ms
Long term stabilit y 20 mbar/yr
Temperature Min Typ Max Unit
Range -40 +85 °C
Resolution 0.005 0.015 °C
Accuracy -0.8 +0.8 °C
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PERFORMANCE SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
Parameter
Symbol
Conditions
Min
Max
Unit
Notes
Supply voltage
VDD
Ta = 25 °C
-0.3
4
V
Storage temperat ure
TS
-40
+85
°C
1
Overpressure
P
Ta = 25 °C
30
bar
2
NOTES
1) Storage and operation in an environment of dry and non-corrosive gases.
2) The MS5 541C is qu alif ied ref erring to the I SO 6425 s tandard and c an withsta nd an abs olute press ure of 30
bar in salt water.
ELECTRICAL CHARACTERISTICS
(Ta = 25 °C, VDD = 3.0 V unless noted otherwise)
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Operating pressure range
p
0
14
bar
Supply voltage
VDD
2.2
3.0
3.6
V
Supply current,
average (1)
during conversion (2)
standby (no conversion)
Iavg
Isc
Iss
V
DD
= 3.0 V
4
1
0.1
µA
mA
µA
Current consumption into MCLK
(3)
MCLK = 32.768 kHz 0.5 µA
Operating temperature range
T
-40
+85
°C
Conversion time
tconv
MCLK = 32.768 kHz
35
ms
Exte rn al clock signal (4)
MCLK
30.000
32.768
35.000
kHz
Duty cycle of MCLK
40/60
50/50
60/40
%
Serial data cloc k
SCLK
500
kHz
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 MS5541C.
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 MS5541C 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.
ANAL OG DIGITAL CONVERTER (ADC)
(T = -40 °C .. 85 °C VDD = 2.2 V .. 3.6 V)
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Resolution
16
Bit
Linear Range
4'000
40'000
LSB
Conversion Time
MCLK = 32.768 kHz
35
ms
INL
Within linear rang e
-5
+5
LSB
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PERFORMANCE SPECIFIC ATIONS (CONTINUED)
PRESSURE OUTPUT CHARACTERISTICS
With the calibration data stored in the interface IC of the MS5541C, the following characteristics can be
achieved: (VDD = 3.0 V unless noted otherwise)
Parameter
Conditions
Min
Typ
Max
Unit
Notes
Resolution
1.2
mbar
1
Absolute Pressure Accuracy
(Temperature range 0 .. +40 °C)
p = 0 .. 5 bar
p = 0 .. 10 bar
p = 0 .. 14 bar
-20
-40
-100
+20
+20
+20
mbar 2
Absolute Pressure Accuracy
(Temperature range -40 .. +85 °C)
p = 0 .. 5 bar
p = 0 .. 10 bar
p = 0 .. 14 bar
-40
-60
-160
+100
+180
+200
mbar 3
Error over Temperature
(p = const. relative to 20 °C)
Ta = -40 .. +85 °C -10 +100 mbar
Long-term Stability
6 months
20
mbar
4
Maximum Error over Supply
Voltage
V
DD
= 2.2 .. 3.6 V
p = const.
-16 16 mbar
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) With the second-or der tem peratur e compensation as des c ribed in Sect ion "FUN C TION". See next section
for typical operating curves.
4) The long-term stability is measured with non-soldered dev ices .
TEMPERATURE OUTPUT CHARA CTERISTICS
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
0.005
0.01
0.015
°C
Accuracy T = 20 °C
P = 0 .. 10bar
-0.8 0.8 °C
T = -40 .. + 85°C
-2
+6
°C
1
Maximum Error over Supply
Voltage
VDD = 2.2 .. 3.6 V -0.2 +0.2 °C 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.
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PERFORMANCE SPECIFIC ATIONS (CONTINUED)
DIGITAL INPUTS
(T = -40 °C .. 85 °C, VDD = 2.2 V .. 3.6 V)
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Input High Voltage
VIH
80% VDD
100% VDD
V
Input Low Voltag e
VIL
0% VDD
20% VDD
V
Signal Rise Time
tr
200
ns
Signal Fall Time
tf
200
ns
DIGITAL OUTPUTS
(T = -40 °C .. 85 °C VDD = 2.2 V .. 3.6 V)
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Output High Voltage
V
OH
I
source
= 0.6 mA
80% V
DD
100% V
DD
V
Output Low Voltage
VOL
Isink = 0.6 mA
0% VDD
20% VDD
V
Signal Rise Time
tr
200
ns
Signal Fall Time
tf
200
ns
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TYPICAL PERFORMANCE CURVES
ADC-value D1 vs Pressure (typical)
10000
15000
20000
25000
30000
02000 4000 6000 8000 10000 12000 14000
Pressure (mbar)
ADC-value D1 (LS B)
-40°C
25°C
85°C
ADC-value D2 vs Temperature ( typical)
15000
20000
25000
30000
35000
40000
-40 -20 020 40 60 80
Temperature (°C)
ADC-value D2 (LSB)
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Absolute Pressure Accuracy after Calibration, 1st order compensation
-100
-50
0
50
100
150
200
250
02000 4000 6000 8000 10000 12000 14000
Pressure (mbar)
Pressure error (mbar)
85°C
60°C
25°C
0°C
-40°C
Absolute Pressure Accuracy after Calibration, 2nd o rder compensati on
-100
-80
-60
-40
-20
0
20
40
60
80
02000 4000 6000 8000 10000 12000 14000
Pressure (mbar)
Pressure error (mbar)
85°C
60°C
25°C
0°C
-40°C
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Temperature Error Accuracy vs temperature (typical)
-5
0
5
10
15
-40 -20 020 40 60 80
Temperat ure (°C)
Temperature error (°C)
Temperature error (standard
calculation)
Temperature error (with 2nd
order calculati on)
Pressure Error Accuracy vs temperature (typical)
-50
-25
0
25
50
75
100
-40 -20 020 40 60 80
Temperature (°C)
Pressure error (mbar)
Pres. error 4bar (1st order)
Pres. error 4bar (2nd order)
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Pressure error vs supply voltage (typical)
-10
-8
-6
-4
-2
0
2
4
6
8
10
2.2 2.4 2.6 2.8 33.2 3.4 3.6
Voltage (V)
Pressure error (mb ar)
14000 mbar
6000 mbar
1000 mbar
Temperature error vs supply voltage (typical)
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
2.2 2.4 2.6 2.8 33.2 3.4 3.6
Voltage (V)
Temperature error (°C)
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FUNCTION
GENERAL
The MS5541C consists of a piezo-resistive sensor and a sensor interface IC. The main function of the MS5541C
is to convert the uncompensated analogue output voltage from the piezo-resistive pressure sensor to a 16-bit
digital value, as well as pro vidin g a 16-bit digital value for the temperature of the sensor.
Measured pressure (16-bit) “D1”
Measured temperature (16-bit) “D2”
As the output voltage of a pressure sensor is strongly dependent on temperature and process tolerances, it is
necessar y to compens ate for thes e effect s. This com pensation proce dure mus t be perform ed by software us ing
an external microcontroller.
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 m odule is indi viduall y factor y calibrated at t wo t em peratures and two press ures. As a result, 6 c oeff icients
necessar y to com pens ate for proces s var iations and t em perature var iat ions ar e calc ulate d and stor ed in the 64-
bit 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 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 MS5541C. 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
temper ature (D2) via the ser ial interface in a loo p (for instance ev ery second). T hen, the com pensated pres sure
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 m ultiplicat ions m ay be u p to 32-b it lon g (+si gn). In the f low accor ding to F ig. 3 a divis ion f ollows e ach
Sensor
D1
D2
Word 1..4
Calculation
in external
micro-
controller
Pressure
Temperature
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multiplication. 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".
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System
initialisation
Pressure and temperature measurement
Example:
Word1, Word2, Word3 and Word4 (4x16 Bit)
D1 = 17788
D2 = 26603
Start
Convert calibration data into coefficients:
(see bit pattern of Word1-Word4)
Read calibration data (factory calibrated) from
PROM of MS5541C
Read digital pressure value from MS5541C
D1 (16 Bit)
Read digital temperature value from MS5541C
Display pressure and temperature value
Basic equations:
Calculate calibration temper ature
UT1=8*C5+10000
Calculate tem perat ur e co mpensated pressure
Difference between actual temperature and reference
temperature:
dT = D2 - UT1
Actual tem pe ra tur e:
TEMP = 200 + dT*(C6+100)/2
11
(0.1°C)
Calculate act ual tem perat ur e
D2 (16 Bit)
SENST1
OFFT1
TCS
TCO
T
ref
TEMPSENS
C1: Pressure sensitivity (13 Bit)
C2: Pressure offset (13 Bit)
C3: Temperature coefficient of pressure sensitivity (10 Bit)
C4: Temperature coefficient of pressure offset (9 Bit)
C5: Reference Temperature (12 Bit)
C6: Temperature coefficient of the temperature (7 Bit)
(
Refer to applicati on note AN518 for limits of coefficients and
calculated results)
Word1 = 18556
Word2 = 49183
Word3 = 22354
Word4 = 28083
C1 = 2319
C2 = 4864
C3 = 349
C4 = 219
C5 = 2002
C6 = 51
dT(D2) = D2 - T
ref
TEMP(D2)=20°+dT(D2)*TEMPSENS
Offset at actual temperature:
OFF = C2 + ((C4-250)*dT)/2
12
+ 10000
Sensitivity at actual temperature:
SENS = C1/2 + ((C3+200)*dT)/2
13
+ 3000
Temperature compensated pressure in mbar:
P = (SENS * (D1-OFF))/2
12
+ 1000
OFF(D2)=OFFT1+TCO*dT(D2)
SENS(D2)=SENST1+TCS*dT(D2)
P(D1,D2)=D1*SENS(D2)-OFF(D2)
dT = 587
TEMP = 243
= 24.3 °C
OFF = 14859
SENS = 4198
P = 4001
= 4001 mbar
UT1 = 26016
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 1 mbar resolution, it is recommended to display the average of 8 subsequent
pressure values.
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C1 (13 Bit)
C2/I (3 Bit)
Word 1 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB12 DB11 DB10
C2/II (10 Bit)
C5/I (6 Bit)
Word 2 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB11 DB10 DB9 DB8 DB7 DB6
C3 (10 Bit)
C5/II (6 Bit)
Word 3 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB5 DB4 DB3 DB2 DB1 DB0
C4 (9 Bit)
C6 (7 Bit)
Word 4 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB1 DB6 DB5 DB4 DB3 DB2 DB1 DB0
Fig. 4: Arrangement (Bit-pattern) of calibration data in Word1 to Word4
SECOND-ORDER TEMPERATURE COMPENSATION
In order to obtain full temperature accuracy over the whole temperature range, it is recommended to
compens ate f or the n on-l inear ity of the outp ut of t he t e mperature s ens or. This can be ac hi ev ed by correcti ng t he
calculated temperature and pressure by a second order correction factor. The second-order factors are
calculated as follows:
High Temperatures
dT2 = dT – (dT/128*dT/128)/8
dT < 0
yes
Calculate temperature
TEMP = (200 + dT2*(C6+100)/2
11
) (0.1°C)
Low Temperatures
dT2 = dT – (dT/128*dT/128)/2
dT ≥ 0
yes
Fig. 5: Flow chart for calculating the temperature and pressure to the optimum accuracy.
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SERIAL INTERFACE
The MS5541C 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 synchronizes the
data trans fer with each bit bei ng sampled b y the MS5 541C on the rising edg e of SCLK and eac h bit being sent
by the MS5541C on the rising edge of SCLK. The data should thus be sampled by the microcontroller on the
falling edg e of SCLK and s ent to the M S5541C with the f alling edge of SCLK. T he SCLK-s ignal is gen erated by
the microprocessor’s system. The digital data provided by the MS5541C 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 t he conversi on status (conversion-r eady signa l, see belo w). The selec tion 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 “D1” (Figure 6a)
• Conversion start for temperature measurement and ADC-data-out “D2” (Figure 6b)
• Calibration data read-out sequence for Word1 (Figure 6c)
• Calibration data read-out sequence for Word2 (Figure 6d)
• Calibration data read-out sequence for Word3 (Figure 6c)
• Calibration data read-out sequence for Word4 (Figure 6d)
• RESET sequence (Figure 6e)
Every communication starts with an instruction sequence at pin DIN. Fig. 6 shows the timing diagrams for the
MS5541C. 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 temperat ur e- (D2) r ead in g th e module acknowledges t he start o f a conver si on by a lo w to h igh
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 m icrocontroller. The microcontroller ma y now read out the
16 bit word b y giving a not h er 17 cloc ks on the SLCK p in. It is pos s ible to i nter rup t t he dat a RE ADO UT s equenc e
with a hol d of the SCLK s ignal. It is important to always read out the last conversion result before starting
a new conversion.
The RESET sequence is special as the module in any state recognizes its unique pattern. By consequence, it
can be used to restart if synchronization between the microcontroller and the MS5541C has been lost. This
sequence is 21-bit long. T he DOUT signal m ight change duri ng that seq uence (s ee Fig. 6e). It is recom mended
to send the RESET sequence before each CONVERSION sequence to avoid hanging up the protocol
permanently in case of electrical interference.
sequence: START+P-measurement
SCLKDOUTDIN
Bit7
Conversion start for pressure measurement and ADC-data-out "D1":
end of convers ion
Bit6Bit5Bit4Bit3Bit2Bit1Bit0
conversion
(33ms)
DB7
ADC-data ou t MSB ADC-data out LSB
Bit8 Bit9
Start-bit Stop-bit
DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
start of conversion
Setup-bits
Fig. 6a: D1 ACQUISITION sequence
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sequence: START+T-measurement
SCLK
DOUT
DIN
Bit7
Conversion start for temperature measurement and ADC-data-out "D2":
end of convers ion
Bit6Bit5Bit4Bit3Bit2Bit1Bit0
conversion
(33ms)
Bit8 Bit9
Start-bit Stop-bit
Setup-bits
start of conversion
DB7
ADC-data ou t MSB ADC-data out LSB
DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
Fig. 6b: D2 ACQUISITION sequence
sequence: coefficient read + addr ess
SCLK
DOUTDIN
Bit7
Calibration data read out sequence for word 1/ word 3:
Bit6Bit5Bit4Bit3Bit2Bit1Bit0
DB7
coefficient-data out MSB coefficient-data o ut LSB
Bit8 Bit9
Start-bit Stop-bit
DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
Bit10 Bit11
address word 1
address word 3
Setup-bits
Fig. 6c: Word1, Word3 READING sequence
address word 2
address word 4
sequence: coefficient read + addr ess
SCLK
DOUT
DIN
Bit7
Calibration data read out sequence for word 2/ word 4:
Bit6Bit5Bit4Bit3Bit2Bit1Bit0
DB7
coefficient-data out MSB coefficient-data o ut LSB
Bit8 Bit9
Start-bit Stop-bit
DB6 DB5 DB4 DB3 DB2 DB1 DB0 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
Bit10 Bit11
Setup-bits
Fig. 6d: W2, W4 READIN G sequence
sequence: RESET
SCLKDOUTDIN
Bit7
RESET - sequence:
Bit6Bit5Bit4Bit3Bit2Bit1Bit0 Bit8 Bit9 Bit10 Bit11Bit12 Bit13 Bit14 Bit15 Bit16 Bit17Bit18 Bit19 Bit20
Fig. 6e: RESET sequence (21 bit)
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APPLICATION INFORMATION
GENERAL
The advant age f or this c om binat ion of a sensor with a direc tly adapted int egrat ed c irc uit is t o save o ther 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
automot ive ap pl icati ons . The possib il ity to compens at e the s ensor with s of t ware a l lo ws th e user to a dap t it t o his
particular application. Communication between the MS5541C 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 ther e are no spe cif ic standard inter face c ells r equired, wh ich m ay be of interes t for spec ially desig ned
4 Bit-microcontroller applications.
CALIBRATION
The MS5541C 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 MS5541C carries a metal protection cap filled with silicone gel for enhanced protection
against humidit y. The pr op erties of this ge l ens ur e f unc tion of the sensor ev en when in direc t water c ont ac t. T his
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 g el surfac e. In this c ase it is better to rinse with clean water aft erwards. Spec ial car e 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 m etal protection cap is fabr icated of special antic orrosive and antim agnetic stain less steel in order to a void
any corrosive battery effects inside the final product. The MS5541C was qualified referring to the ISO 6425
standard and can withstand a pressure of 30 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 under water op erations lik e specif ied in ISO 6 425 s tandar d it is im port ant to seal th e sens or with a r ubber O-
Ring around the metal Ring. An y salt water com ing to the contact side (ceramic and Pads) of the sensor could
lead to permanent damage. For "water-resistant" 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 MS5541C 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.
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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 applicat ions subjected to m echanical shock, it is recomm ended to enhance the mechanical reliability of the
solder junctions by covering the rim or the corners of MS5541C's ceramic substrate with glue or Globtop-like
material.
DECOUPLING CAPACITOR
Particular c ar e must be taken when c o nnec t ing the de vice to p ower supply. A 47 µF t anta lum capacitor must be
placed as close as possible of the MS5541C's VDD pin. This capacitor will stabilize the power supply during
data convers ion and thus, prov ide the hi ghest pos s ib le acc uracy.
APPLI CATION EXAMPLE: DIVING COMPUTER SYSTEM USING MS5541C
MS5541C is a circuit th at can be use d in connecti on with a m icrocontroller i n diving computer applicat ions. It is
designed for lo w-voltage s ystem s with a sup pl y voltage of 3V, p articu larl y in batt er y applicat ions. T he MS554 1C
is optim ised for low current consum ption 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 MEAS Switzerland 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.
4/8bit-Microcontroller
LCD-Display
EEPROM
Keypad
MS5541C
SCLK
DIN
DOUT
MCLK
XTAL1
XTAL2
32.768 kHz
optional
VDD
GND
VDD
GND
3V-Battery
47µF
Tantal
Figure 7: Demonstration of MS5541C in a diving computer
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PIN CONFIGURATION
Fig. 2: Pin configuration of MS5541C
Pin Name
Pin
Type
Function
SCLK
1
I
Serial data cloc k
GND
2
G
Ground
PV (1)
3
N
Negative programming voltage
PEN (1)
4
I
Programming enable
VDD
5
P
Positive supply voltage
MCLK
6
I
Master clock (32.768 kHz)
DIN
7
I
Serial data input
DOUT
8
O
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.
RECOMMENDED PAD LAYOUT
Pad layout for bottom side of MS5541C soldered onto printed circuit board.
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DEVICE PACKAGE OUTLINES
Fig. 8: Device package outlines of MS5541-C
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ASSEMBLY
ME CHANI CAL STRESS
It is recom mended to avoid m ec hanical s tr ess on t he PCB on wh ich th e s ens or is mounted. The thic k nes s 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 MS5541C 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.
The MS5541C can be mounted with the cap down or the cap looking upwards. In both cases it is important to
solder all co ntact p ads. T he Pins PEN an d PV sha ll be lef t open or c onnec ted 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 M S5 541-CM pr ovides the p os sibi lity to seal with an O -r ing . T he pr ote c tive cap of the M S5 541CM is
made of special anticorrosive stainless steel with a polished surface. In addition to this the M S5541CM is filled
with silico ne gel cover ing the sens or and the b onding wires . The O -ring (or O-rings ) shall be plac ed at the outer
diameter of the metal cap. This method avoids mechanical stress because the sensor can move in vertical
direction.
CLEANING
The MS5541C 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 ass embl y from entering par ticles and d ust. To avo id cleaning of the PCB, s older 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
essentia l to ground machin es and p er sonal pr o perly dur ing ass embly and han dl in g of the d ev ice. The MS5541C
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.
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ORDERING INFORMATION
Part Number / Art. Number
Product
Delivery Form
325541009-00
MS5541C Miniature 14 bar Module White gel
Tube
325541009-50
MS5541C Miniature 14 bar Module White gel T&R
Tape& reel TOP-UP
325541008-00
MS5541C Miniature 14 bar Module Transparent gel
Tube
325541008-50
MS5541C Miniature 14 bar Module Transparent gel T&R
Tape& reel TOP-UP
325541021-00
MS5541C Miniature 14 bar Module Transparent gel HE
Tube
325541021-50
MS5541C Miniature 14 bar Module Transparent gel HE T&R
Tape& reel TOP-UP
FACTORY CONTACTS
NORTH AMERICA
EUROPE
ASIA
Measurement Specialties
45738 Northport Loop West
Fremont, CA 94538
Tel: +1 800 767 1888
Fax: +1 510 498 1578
e-mail: pfg.cs.amerameas-spec.com
Website: www.meas-spec.com
MEAS Switzerland Sàrl
Ch. Chapons-des-Prés 11
CH-2022 Bevaix
Tel: +41 32 847 9550
Fax: + 41 32 847 9569
e-mail: sales.chameas-spec.com
Website: www.meas-spec.com
Measurement Specialties (China), Ltd.
No. 26 Langshan Road
Shenzhen High-Tech Park (North)
Nanshan District, Shenzhen, 518057
China
Tel: +86 755 3330 5088
Fax: +86 755 3330 5099
e-mail: pfg.cs.asiaameas-spec.com
Website: www.meas-spec.com
The information in this sheet has been carefull y reviewed and is believed to be accurate; however, no responsibility is assumed for
inaccuracies. Furtherm ore, this inform ation does not convey to the purchaser of such devices any license under the patent rights to the
manufacturer. Measurem ent Specialt i es, Inc. reserves the right t o make changes without furt her notice to any product herein. Measurement
Specialti es, Inc. makes no warranty, represent ation or guarant ee regarding the sui t abili t y of its product for any particular purpose, nor does
Measurement Specialti es, Inc. assume any liability arising out of the application or use of any product or circuit and specifically disclaims
any and all liabilit y, includi ng without limitation consequential or incidental damages. Typical parameters can and do vary in different
applicat i ons. All operat i ng parameters must be validated for each customer application by customer’s technical experts. Measurement
Specialti es, Inc. does not convey any license under its patent rights nor the rights of others.
