The SMD500 marks a new generation of high precision digital
pressure sensors for consumer applications.
Its ultra low-power, low voltage electronics are optimized for
use in mobile phones, PDAs, GPS devices and outdoor
equipment. With an altitude noise down to 0.25 m it offers
superior performance. The I
2
C interface allows for easy
system integration with a microcontroller.
Robert Bosch is the world market leader for pressure sensors
in automotive applications. Based on the experience of over
100 million pressure sensors in the field, the SMD500 opens
a new generation of micromachined pressure sensors.
Typical Applications
Outdoor navigation
Dead reckoning
Leisure and sports
Weather forecast
Vertical velocity indication (rise / sink speed)
Security systems
The SMD500 is based on piezoresistive technology for EMC
robustness, high accuracy and linearity as well as long term
stability.
Altimeter / Barometer SMD500
Key Features
Pressure range
Supply voltage
Current consumption
Resolution
(rms noise)
Sigma delta ADC
Fully calibrated
Temperature measurement included
Digital two wire I C interface
Lead free and RoHS compliant
2
Altitude above Sea Level vs. Barometric Pressure
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
-1000
30
0
40
0
50
0
60
0
70
0
300 ... 1100 hPa (+9000 ... -500 m)
2.2 ... 3.6 V
5 µA (std. avg. @ 1 sample / sec.)
10 µA (high resolution)
±0.06 hPa (0.5 m) std. resolution
±0.03 hPa (0.25 m) high resolution
Altitude above sea level [m]
Altitude in standard
atmosphere
10
00
Barometric pressure [hPa]
11
00
1
Bosch Sensortec GmbH reserves all rights in the event of industrial property rights. We reserve all rights of disposal such as copying and passing on to third parties.
BOSCH and the symbols are registered trademarks of Robert Bosch GmbH, Germany.
80
0
90
0
Absolute Maximum Ratings
Storage temperature
Supply voltage
ESD Rating (HBM)
Overpressure
-40 ... +125 °C
-0.3 ... 6.0 V
±2 kV
5000 hPa
SMD500 pinout configuration
Top view LCC8 ceramic package
3
dimensions: 5.0 x 5.0 (± 0.25) x 1.55 mm (± 0.15).
Operating Conditions
Temperature, operational
full accuracy
Supply voltage VDD
Standby current
Avg. current consumption
@ 1Hz data refresh rate
Pressure range
RMS noise expressed in
pressure
RMS noise expressed in
altitude (@ 1 conversion)
Absolute accuracy
@ p = 700 ... 1100 hPa,
0 ... +65°C, VDD = 3.3 V,
MCLK = 32768 Hz
Serial data clock
Master clock frequency
(selectable)
Pressure conversion time
-40 ... +85 °C
0 ... +65 °C
2.2 ... 3.6 V; typ 3.3 V
0.7 µA typ.
5 µA typ. standard mode
10 µA typ. high res. mode
300 ... 1100 hPa
0.06 hPa typ. standard
0.03 hPa typ. high res.
0.5 m typ. standard
0.25 m typ. high res.
pressure: ±2.5 hPa max.
±0.8 hPa typ.
temperature: ±2°C max.
max. 400 kHz
32768 Hz ± 3 %
or 1 MHz ± 3 %
34 ms @ 32768 Hz
Pinout
1
2
3
4
The SMD500 is designed to be connected directly to a
microcontroller of a mobile device via the I
2
C bus.
The pressure and temperature data comes as 16 bit each and
has to be compensated by the calibration data of the PROM
of the SMD500.
5
6
7
8
GND
NC
VDDA
VDDD
MCLK
SCL
SDA
XCLR
ground
do not connect
power supply analog
power supply digital
master clock input
I
2
C serial bus clock input
I
2
C serial bus data
master clear (low active) input
Bosch Sensortec GmbH
Bosch Sensortec is a newly founded subsidiary of Bosch.
It focuses on application and marketing of micromechanical
components for all markets except the automotive.
Please contact us for further details.
Gerhard-Kindler-Strasse 8
72770 Reutlingen, Germany
Leopold.Beer@bosch-sensortec.com
www.bosch-sensortec.com
Modifications reserved | Printed in Germany
Version_1.5_070313 – sensor data may be subject to
change before final release; This datasheet V1.5 is valid
for engineering samples with date codes: *4934 - *8040
2
and from *9207 on.
Bosch Sensortec GmbH reserves all rights in the event of industrial property rights. We reserve all rights of disposal such as copying and passing on to third parties.
BOSCH and the symbols are registered trademarks of Robert Bosch GmbH, Germany.
2. General Function and application schematics
The SMD500 consists of a piezoresistive sensor, an analog to digital converter, control unit with PROM and a serial I
2
C interface.
The SMD500 converts the uncompensated value of pressure and temperature from the pressure sensor and has stored 64 bit of
individual calibration data in a PROM. This calibration data is used to compensate offset, temperature dependence etc. of the
sensor.
pressure data word (16 bit word, 16 bit resolution)
UP
temperature data word (16 bit word, 16 bit resolution)
UT
The SMD500 is designed to be connected directly to a microcontroller of a mobile device via the I
2
C interface.
2.2 … 3.6 V
100 nF
4.7 µF
+
VDDA
PROM
SMD500
VDDD
µController
e. g. 8 bit
R
p
(1)
R
p
(1)
SDA
Control
Unit
SCL
XCLR
I
2
C
interface
Sensor
element
ADC
MCLK
32768 Hz or
1 MHz
(register option)
GND
Note:
(1) Pull-up resistors for I
2
C bus, R
p
= 2.2 kΩ … 10 kΩ, typ. 4.7 kΩ
Display
Figure 1: Typical application circuit
To guarantee conversion accuracy two supply voltage decoupling capacitors of 4.7 µF and 100 nF should be placed between
VDD and GND of the SMD500.
3
Bosch Sensortec GmbH reserves all rights in the event of industrial property rights. We reserve all rights of disposal such as copying and passing on to third parties.
BOSCH and the symbols are registered trademarks of Robert Bosch GmbH, Germany.
3. Measurement of pressure and temperature
The steps to measure pressure and temperature data and calculation of the physical values are shown in the following figures.
For all calculations presented here an ANSI C code is available.
To start a pressure or temperature measurement the microcontroller sends a start sequence. After the conversion time the result
value (UT or UP) can be read via the I
2
C interface. For calculating the temperature in °C and pressure in hPa the calibration data
is used. These constants can be read out from the SMD500 PROM once at software start-up.
The sampling rate can be increased up to 14 samples per second for dynamic measurement or to average out noise. In this case,
it is sufficient to measure the temperature only once per second and use this value for all pressure measurements in this period.
Using oversampling and averaging, the optimum compromise between power consumption, speed and resolution can be
selected, see table 1.
Table 1: Relation between averaging, power consumption, speed and resolution (at sea level).
mode
standard
high
resolution
high speed
pressure
measurements
per sec
1
4
10
number of
averages
1
4
1
temperature
measurements
per sec
1
1
1
data refresh
rate [Hz]
1
1
10
avg. current
consumption
[µA]
5
10
25
RMS noise
[hPa]
0.06
0.03
0.06
RMS noise
[m]
0.5
0.25
0.5
Start
start temperature
measurement
wait 34 ms
read UT
start pressure
measurement
wait 34 ms
read UP
Repeat if averaging is
requested
calculate pressure and
temperature in physical
units
Figure 2: Flow chart temperature and pressure measurement
4
Bosch Sensortec GmbH reserves all rights in the event of industrial property rights. We reserve all rights of disposal such as copying and passing on to third parties.
BOSCH and the symbols are registered trademarks of Robert Bosch GmbH, Germany.
3.1. Calibration coefficients
The 64 bit PROM is partitioned in four words F1 to F4 of 16 bit each. These 64 bits contain six calibration coefficients AC1 to AC6
as shown in table 2. Each sensor module has individual coefficients. Before the first calculation of temperature and pressure, the
master reads out the PROM data words F1 to F4 and converts them into the six calibration coefficients AC1 to AC6 using the C
code function SMD500_convertPROMdata.
Then the function SMD500_init_calB1B2 calculates the two derived coefficients B1 and B2 as shown in figure 3.
Table 2: PROM mapping of the six coefficients AC1 to AC6
bit 15
F1
F2
F3
F4
AC2_1
AC2_8
AC5_2
AC5_6
bit 14
AC2_0
AC2_7
AC5_1
AC5_5
bit 13
bit 12
bit 11
bit 10
bit 9
AC1_9
AC2_2
AC4_9
AC6_9
bit 8
AC1_8
AC3_8
AC4_8
AC6_8
bit 7
AC1_7
AC3_7
AC4_7
AC6_7
bit 6
AC1_6
AC3_6
AC4_6
AC6_6
bit 5
AC1_5
AC3_5
AC4_5
AC6_5
bit 4
AC1_4
AC3_4
AC4_4
AC6_4
bit 3
AC1_3
AC3_3
AC4_3
AC6_3
bit 2
AC1_2
AC3_2
AC4_2
AC6_2
bit 1
AC1_1
AC3_1
AC4_1
AC6_1
bit 0
AC1_0
AC3_0
AC4_0
AC6_0
AC1_13 AC1_12 AC1_11 AC1_10
AC2_6
AC5_0
AC5_4
AC2_5
AC2_4
AC2_3
AC4_12 AC4_11 AC4_10
AC5_3
AC6_11 AC6_10
St art
example:
Read calibrat ion dat a
from t he PROM of t he SMD500
F1, F2, F3, F4
(4 x 16 bit )
F1 =
F2 =
F3 =
F4 =
Convert calibrat ion dat a int o calibrat ion
coefficient s (see t able 2)
AC1
(14
AC2
(9
AC3
(9
AC4
(13
AC5
(7
AC6
(12
40851
29891
21009
38946
C code funct ion:
SMD500_convert PROMdat a
bit )
bit )
bit )
bit )
bit )
bit )
AC1
AC2
AC3
AC4
AC5
AC6
=
=
=
=
=
=
8083
234
195
4625
74
2082
calculat e coefficient B1 and B2
B1 = ((AC3 - 1984) * (-17268)) / 2
11
- 8970
B2 = ((AC2 - 457) * B1 / 2 ) / (AC3 - 1984)
Figure 3: Initial calculations for the SMD500
4
B1 =
B2 =
6114
47
SMD500_init _calB1B2
3.2. Calculating pressure and temperature
The calculation of temperature in °C and pressure in Pa is shown in figure 4. This corresponds to the C code functions
SMD500_caltemperature, SMD500_calB3, SMD500_calB4 and SMD500_calpressure.
5
Bosch Sensortec GmbH reserves all rights in the event of industrial property rights. We reserve all rights of disposal such as copying and passing on to third parties.
BOSCH and the symbols are registered trademarks of Robert Bosch GmbH, Germany.
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