MS5637-02BA03 Low Voltage Barometric Pressure Sensor
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• QFN package 3 x 3 x 0.9 mm3
• High-resolution module, 13 cm
• Supply voltage: 1.5 to 3.6 V
• Fast conversion down to 0.5 ms
• Low power, 0.6 µA (standby < 0.15 µA at 25°C)
• Integrated digital pressure sensor (24 bit ΔΣ ADC)
• Operating range: 300 to 1200 mbar, -40 to +85 °C
• I2C interface
• No external components (internal oscillator)
DESCRIPTION
The MS5637 is an ultra-compact micro altimeter. It is optimized for altimeter and barometer applications in
Smart-phones and Tablet PCs. The altitude resolution at sea level is 13 cm of air. The sensor module includes a
high-linearity pressure sensor and an ultra-low power 24 bit ΔΣ ADC with internal factory-calibrated coefficients.
It provides a precise digital 24-bit pressure and temperature value and different operation modes that allow the
user to optimize for conversion speed and current consumption. A high-resolution temperature output allows the
implementation of an altimeter/thermometer function without any additional sensor. The MS5637 can be
interfaced to any microcontroller with I2C-bus interface. The communication protocol is simple, without the need
of programming internal registers in the device. Small dimensions of 3 x 3 x 0.9 mm3 allow the integration in
mobile devices. This new sensor module generation is based on leading MEMS technology and latest benefits
from MEAS Switzerland proven experience and know-how in high volume manufacturing of altimeter modules,
which has been widely used for over a decade. The sensing principle employed leads to very low hysteresis and
high stability of both pressure and temperature signal.
FEATURES
FIELD OF APPLICATION TECHNICAL DATA
Smart-phones Sensor Performances (VDD = 3 V)
Tablet PCs Pressure Min Typ Max Unit
Personal navigation devices Maximum Range 10 2000 mbar
FUNCTIONAL BLOCK DIAGRAM
VDD
GND
SCL
SDA
ADC
I2C Bus
Interface
Memory
(PROM)
112 bits
SENSOR
SGND
+IN
-IN
dig.
Filter
Sensor
Interface IC
ADC 24 bit
Resolution (1)
0.11 / 0.062/ 0.039
/ 0.028 / 0.021 /
0.016
mbar
Error band at 25°C,
300 to 1200 mbar -2 +2 mbar
Error band, -20°C to + 85°C
300 to 1200 mbar (2) -4 +4 mbar
Response time (1) 0.5 / 1.1 / 2.1 / 4.1 / 8.22 / 16.44 ms
Long term stability ±1 mbar/yr
Temperature Min Typ Max Unit
Range -40 +85 °C
Resolution <0.01 °C
Accuracy at 25°C -1 +1 °C
Notes: (1) Oversampling Ratio: 256 / 512 / 1024 / 2048 / 4096 / 8192
(2) With auto-zero at one pressure point
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PERFORMANCE SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
Parameter Symbol Conditions Min. Typ. Max. Unit
Supply voltage VDD -0.3 +3.6 V
Storage temperature TS -20 +85 °C
Overpressure Pmax 6 bar
Maximum Soldering
Temperature Tmax 40 sec max 250 °C
ESD rating Human Body Model -2 +2 kV
Latch up JEDEC standard No 78 -100 +100 mA
ELECTRICAL CHARACTERISTICS
Parameter Symbol Conditions Min. Typ. Max. Unit
Operating Supply voltage VDD 1.5 3.0 3.6 V
Operating Temperature T -40 +25 +85 °C
Supply current
(1 sample per sec.)
IDD
OSR 8192
4096
2048
1024
512
256
20.09
10.05
5.02
2.51
1.26
0.63
µA
Peak supply current during conversion 1.25 mA
Standby supply current at 25°C (VDD = 3.0 V) 0.01 0.14 µA
VDD Capacitor from VDD to GND 100 470 nF
ANALOG DIGITAL CONVERTER (ADC)
Parameter Symbol Conditions Min. Typ. Max. Unit
Output Word 24 bit
Conversion time tc
OSR 8192
4096
2048
1024
512
256
16.44
8.22
4.13
2.08
1.06
0.54
ms
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MS5637-02BA03 Low Voltage Barometric Pressure Sensor
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PERFORMANCE SPECIFICATIONS (CONTINUED)
PRESSURE OUTPUT CHARACTERISTICS (VDD = 3.0 V, T = 25 °C UNLESS OTHERWISE NOTED)
Parameter Conditions Min. Typ. Max. Unit
Operating Pressure Range Prange 300 1200 mbar
Extended Pressure Range Pext
Linear Range of
ADC 10 2000 mbar
Relative Accuracy, autozero at
one pressure point (1) 700…1000 mbar at 25°C ±0.1 mbar
Absolute Accuracy,
no autozero
300..1200 mbar at 25°C
300..1200mbar, -20..85°C
-2
-4
+2
+4
mbar
Resolution RMS
OSR 8192
4096
2048
1024
512
256
0.016
0.021
0.028
0.039
0.062
0.11
mbar
Maximum error with supply
voltage VDD = 1.5 V … 3.6 V ±0.5 mbar
Long-term stability ±1 mbar/yr
Reflow soldering impact
IPC/JEDEC J-STD-020C
(See application note AN808
on http://meas-spec.com)
-1 mbar
Recovering time after reflow (2) 3 days
(1) Characterized value performed on qualification devices
(2) Recovering time at least 66% of the reflow impact
TEMPERATURE OUTPUT CHARACTERISTICS (VDD = 3 V, T = 25°C UNLESS OTHERWISE NOTED)
Parameter Conditions Min. Typ. Max. Unit
Absolute Accuracy
at 25°C
-20..85°C
-1
-2
+1
+2
°C
Maximum error with supply
voltage VDD = 1.5 V … 3.6 V ±0.3 °C
Resolution RMS
OSR 8192
4096
2048
1024
512
256
0.002
0.003
0.004
0.006
0.009
0.012
°C
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MS5637-02BA03 Low Voltage Barometric Pressure Sensor
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PERFORMANCE SPECIFICATIONS (CONTINUED)
DIGITAL INPUTS (SDA, SCL)
Parameter Symbol Conditions Min. Typ. Max. Unit
Serial data clock SCL 400 kHz
Input high voltage VIH 80% VDD 100% VDD V
Input low voltage VIL 0% VDD 20% VDD V
Input leakage current I leak T = 25 °C 0.14 µA
Input capacitance CIN 6 pF
DIGITAL OUTPUTS (SDA)
Parameter Symbol Conditions Min. Typ. Max. Unit
Output high voltage VOH Isource = 1 mA 80% VDD 100% VDD V
Output low voltage VOL Isink = 1 mA 0% VDD 20% VDD V
Load capacitance CLOAD 16 pF
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FUNCTIONAL DESCRIPTION
VDD
GND
SCL
SDA
ADC
I2C Bus
Interface
Memory
(PROM)
112 bits
SENSOR
SGND
+IN
-IN
dig.
Filter
Sensor
Interface IC
Figure 1: Block diagram
GENERAL
The MS5637 consists of a piezo-resistive sensor and a sensor interface integrated circuit. The main function of
the MS5637 is to convert the uncompensated analogue output voltage from the piezo-resistive pressure sensor
to a 24-bit digital value, as well as providing a 24-bit digital value for the temperature of the sensor.
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
112-bit PROM of each module. These bits (partitioned into 6 coefficients) must be read by the microcontroller
software and used in the program converting D1 and D2 into compensated pressure and temperature values.
SERIAL I2C INTERFACE
The external microcontroller clocks in the data through the input SCL (Serial CLock) and SDA (Serial DAta). The
sensor responds on the same pin SDA which is bidirectional for the I2C bus interface. So this interface type uses
only 2 signal lines and does not require a chip select.
Module reference Mode Pins used
MS563702BA03 I2C SDA, SCL
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PRESSURE AND TEMPERATURE CALCULATION
Size [1]
[bit] min max
C1 Pressure sensitivity | SENST1 unsigned int 16 16 0 65535 46372
C2 Pressure offset | OFFT1 unsigned int 16 16 0 65535 43981
C3 Temperature coefficient of pressure sensitivity | TCS unsigned int 16 16 0 65535 29059
C4 Temperature coefficient of pressure offset | TCO unsigned int 16 16 0 65535 27842
C5 Reference temperature | TREF unsigned int 16 16 0 65535 31553
C6 Temperature coefficient of the temperature | TEMPSENS unsigned int 16 16 0 65535 28165
D1 Digital pressure value unsigned int 32 24 0 16777216 6465444
D2 Digital temperature value unsigned int 32 24 0 16777216 8077636
dT
Difference between actual and reference temperature [2]
dT = D2 - TREF = D2 - C5 * 2
8 signed int 32 25 -16776960 16777216 68
2000
= 20.00 °C
OFF
Offset at actual temperature [3]
OFF = OFFT1 + TCO * dT = C2 * 2
17
+ (C4 * dT ) / 26
signed int 64 41 -17179344900 25769410560 5764707214
SENS
Sensitivity at actual temperature [4]
SENS = SENST1 + TCS * dT = C1 * 2
16
+ (C3 * dT ) / 27
signed int 64 41 -8589672450 12884705280 3039050829
110002
= 1100.02 mbar
Notes
[1]
[2]
[3]
[4]
min and max have to be defined
min and max have to be defined
Maximal size of intermediate result during evaluation of variable
120000100058P
Recommended
variable typeDescription | Equation
signed int 32
Actual temperature (-40…85°C with 0.01°C resolution)
TEMP = 20°C + dT * TEMPSENS = 2000 + dT * C6 / 223
Read digital pressure and temperature data
signed int 32
Temperature compensated pressure (10…1200mbar with
0.01mbar resolution)
P = D1 * SENS - OFF = (D1 * SENS / 2 21 - OFF) / 2 15
min and max have to be defined
Convert calibration data into coefficients (see bit pattern of W1 to W4)
Variable Example / Typical
Value
Calculate temperature compensated pressure
8500-4000TEMP 41
Start
Maximum values for calculation results:
PMIN = 10mbar PMAX = 2000mbar
TMIN = -40°C TMAX = 85°C TREF = 20°C
Read calibration data (factory calibrated) from PROM
Read digital pressure and temperature data
Calculate temperature
Calculate temperature compensated pressure
Display pressure and temperature value
Figure 2: Flow chart for pressure and temperature reading and software compensation.
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MS5637-02BA03 Low Voltage Barometric Pressure Sensor
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SECOND ORDER TEMPERATURE COMPENSATION
In order to obtain best accuracy over temperature range, particularly at low temperature, it is recommended to
compensate the non-linearity over the temperature. This can be achieved by correcting the calculated
temperature, offset and sensitivity by a second-order correction factor. The second-order factors are calculated
as follows:
Figure 3: Flow chart for pressure and temperature to the optimum accuracy.
Yes No
SENS2 = 29 ⋅ (TEMP – 2000)2/ 24
SENS2 = 0
SENS = SENS - SENS2
TEMP<20°C
Low temperature
T2 = 3 ⋅ dT 2 / 2 33
OFF2 = 0
T2 = T2 = 5 ⋅ dT
2 / 2
38
OFF2 = 61 ⋅ (TEMP – 2000)2 / 24
OFF = OFF - OFF2
TEMP = TEMP - T2
Low temperature High temperature
Calculate pressure and temperature
TEMP<-15°C
No Yes
SENS2 = SENS2 + 9 ⋅ (TEMP + 1500)2
Low temperature
OFF2 = OFF2 + 17 ⋅ (TEMP + 1500)2
Very low temperature
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I2C INTERFACE
COMMANDS
The MS5637 has only five basic commands:
1. Reset
2. Read PROM (112 bit of calibration words)
3. D1 conversion
4. D2 conversion
5. Read ADC result (24 bit pressure / temperature)
Each I2C communication message starts with the start condition and it is ended with the stop condition. The
MS5637 address is 1110110x (write : x=0, read : x=1).
Size of each command is 1 byte (8 bits) as described in the table below. After ADC read commands, the device
will return 24 bit result and after the PROM read 16 bit results. The address of the PROM is embedded inside of
the PROM read command using the a2, a1 and a0 bits.
Command byte hex value
Bit number 0 1 2 3 4 5 6 7
Bit name PRO
M
CO
NV
- Typ Ad2/
Os2
Ad1/
Os1
Ad0/
Os0
Stop
Command
Reset 0 0 0 1 1 1 1 0 0x1E
Convert D1 (OSR=256) 0 1 0 0 0 0 0 0 0x40
Convert D1 (OSR=512) 0 1 0 0 0 0 1 0 0x42
Convert D1 (OSR=1024) 0 1 0 0 0 1 0 0 0x44
Convert D1 (OSR=2048) 0 1 0 0 0 1 1 0 0x46
Convert D1 (OSR=4096) 0 1 0 0 1 0 0 0 0x48
Convert D1 (OSR=8192) 0 1 0 0 1 0 1 0 0x4A
Convert D2 (OSR=256) 0 1 0 1 0 0 0 0 0x50
Convert D2 (OSR=512) 0 1 0 1 0 0 1 0 0x52
Convert D2 (OSR=1024) 0 1 0 1 0 1 0 0 0x54
Convert D2 (OSR=2048) 0 1 0 1 0 1 1 0 0x56
Convert D2 (OSR=4096) 0 1 0 1 1 0 0 0 0x58
Convert D2 (OSR=8192) 0 1 0 1 1 0 1 0 0x5A
ADC Read 0 0 0 0 0 0 0 0 0x00
PROM Read 1 0 1 0 Ad2 Ad1 Ad0 0 0xA0 to
0xAE
Figure 4: Command structure
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RESET SEQUENCE
The Reset sequence shall be sent once after power-on to make sure that the calibration PROM gets loaded into
the internal register. It can be also used to reset the device PROM from an unknown condition.
The reset can be sent at any time. In the event that there is not a successful power on reset this may be caused
by the SDA being blocked by the module in the acknowledge state. The only way to get the MS5637 to function
is to send several SCLs followed by a reset sequence or to repeat power on reset.
1 1 1 0 1 1 0 0 0 0 0 0 1 1 1 1 0 0
S W A A P
From Master S = Start Condition W = Write A = Acknowledge
From Slave P = Stop Condition R = Read N = Not Acknowledge
cmd byte
Device Address
Device Address
command
Figure 5: I2C Reset Command
PROM READ SEQUENCE
The read command for PROM shall be executed once after reset by the user to read the content of the
calibration PROM and to calculate the calibration coefficients. There are in total 7 addresses resulting in a total
memory of 112 bit. Addresses contains factory data and the setup, calibration coefficients, the serial code and
CRC. The command sequence is 8 bits long with a 16 bit result which is clocked with the MSB first. The PROM
Read command consists of two parts. First command sets up the system into PROM read mode. The second
part gets the data from the system.
1 1 1 0 1 1 0 0 0 1 0 1 0 0 1 1 0 0
S W A A P
From Master S = Start Condition W = Write A = Acknowledge
From Slave P = Stop Condition R = Read N = Not Acknowledge
Device Address
Device Address cmd byte
command
Figure 6: I2C Command to read memory address= 011
1 1 1 0 1 1 0 1 0 X X X X X X X X 0 X X X X X X X X 0
S R A A N P
From Master S = Start Condition W = Write A = Acknowledge
From Slave P = Stop Condition R = Read N = Not Acknowledage
Memory bit 7 - 0
Device Address
Device Address Memory bit 15 - 8
data data
Figure 7: I2C answer from MS5637
CONVERSION SEQUENCE
The conversion command is used to initiate uncompensated pressure (D1) or uncompensated temperature (D2)
conversion. After the conversion, using ADC read command the result is clocked out with the MSB first. If the
conversion is not executed before the ADC read command, or the ADC read command is repeated, it will give 0
as the output result. If the ADC read command is sent during conversion the result will be 0, the conversion will
not stop and the final result will be wrong. Conversion sequence sent during the already started conversion
process will yield incorrect result as well. A conversion can be started by sending the command to MS5637.
When command is sent to the system it stays busy until conversion is done. When conversion is finished the
data can be accessed by sending a Read command, when an acknowledge is sent from the MS5637, 24 SCL
cycles may be sent to receive all result bits. Every 8 bits the system waits for an acknowledge signal.
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1 1 1 0 1 1 0 0 0 0 1 0 0 1 0 0 0 0
S W A A P
From Master S = Start Condition W = Write A = Acknowledge
From Slave P = Stop Condition R = Read N = Not Acknowledge
cmd byte
Device Address
Device Address
command
Figure 8: I2C command to initiate a pressure conversion (OSR=4096, typ=D1)
1 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0
S W A A P
From Master S = Start Condition W = Write A = Acknowledge
From Slave P = Stop Condition R = Read N = Not Acknowledge
Device Address
Device Address cmd byte
command
Figure 9: I2C ADC read sequence
1 1 1 0 1 1 0 1 0 X X X X X X X X 0 X X X X X X X X 0 X X X X X X X X 0
S R A A A N P
From Master S = Start Condition W = Write A = Acknowledge
From Slave P = Stop Condition R = Read N = Not Acknowledge
Data 7 - 0Data 8 - 15Device Address
Device Address datadata
Data 23-16
data
Figure 10: I2C answer from MS5637
CYCLIC REDUNDANCY CHECK (CRC)
MS5637 contains a PROM memory with 112-Bit. A 4-bit CRC has been implemented to check the data validity
in memory. The application note AN520 describes in detail CRC-4 code used.
A
d
d
D
B
1
5
D
B
1
4
D
B
1
3
D
B
1
2
D
B
1
1
D
B
1
0
D
B
9
D
B
8
D
B
7
D
B
6
D
B
5
D
B
4
D
B
3
D
B
2
D
B
1
D
B
0
0 CRC Factory defined
1 C1
2 C2
3 C3
4 C4
5 C5
6 C6
Figure 11: Memory PROM mapping
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MS5637-02BA03 Low Voltage Barometric Pressure Sensor
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APPLICATION CIRCUIT
The MS5637 is a circuit that can be used in conjunction with a microcontroller in mobile altimeter applications.
Figure 12: Typical application circuit
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PIN CONFIGURATION
Pin Name Type Function
1 VDD P Positive supply voltage
2 SDA I/O I2C data
3 SCL I I2C clock
4 GND I Ground
DEVICE PACKAGE OUTLINE
Notes: (1) Dimensions in mm
(2) General tolerance: ±0.1
Figure 13: MS5637 package outline
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RECOMMENDED PAD LAYOUT
Pad layout for bottom side of the MS5637 soldered onto printed circuit board.
Figure 14: MS5637 pad layout
SHIPPING PACKAGE
Tape and Tape and reel
Reserved area:
Please do not route
tracks between pads
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MOUNTING AND ASSEMBLY CONSIDERATIONS
SOLDERING
Please refer to the application note AN808 available on our website for all soldering issues.
MOUNTING
The MS5637 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.
It is important to solder all contact pads.
CONNECTION TO PCB
The package outline of the module allows the use of a flexible PCB for interconnection. This can be important
for applications in watches and other special devices.
CLEANING
The MS5637 has been manufactured under clean-room conditions. 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 2 kV HBM (human body model). It is therefore
essential to ground machines and personnel properly during assembly and handling of the device.
The MS5637 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.
DECOUPLING CAPACITOR
Particular care must be taken when connecting the device to the power supply. A 100nF minimum ceramic
capacitor must be placed as cl
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