BMA020 Bosch Sensortec, BMA020 Datasheet - Page 47

• Manufacturer Part Number: BMA020
• Description: 3-AXIS ACCELEROMETER DIGITAL I/F
• Manufacturer: Bosch Sensortec

Specifications of BMA020

• Axis: X, Y, Z
• Acceleration Range: ± 2g, 4g, 8g
• Sensitivity: 256LSB/g, 128LSB/g, 64LSB/g
• Voltage - Supply: 2 V ~ 3.6 V
• Output Type: Digital
• Bandwidth: 3kHz
• Interface: I²C, SPI
• Mounting Type: Surface Mount
• Package / Case: 12-LGA
• For Use With: 828-1014 - BMA020 TRIBOX DEMO BOARD W/USB828-1008 - BMA020 DAUGHTERCARD FOR DEV KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 828-1000-2

8. Data conversion
8.1 Acceleration data
Acceleration data are converted by a 10bit ADC. The description of the digital signal is "2’s
complement". The 10 bit data are available as LSB (at lower register address) and MSB. It is
possible to read out MSB only (8 bit) and LSB/MSB (16 bits with 10 data bits and 1 data ready
bit) while LSB- and MSB-data are closely linked to avoid unintentional LSB/MSB mixing when
read out and data conversion overlap accidentally (section 3.5.1).
The update rate of data registers is 3 kHz, independent of the digital filter. The acceleration data
is filtered by a second order analog filter at 1.5 kHz. Additionally the data can be processed by
digital averaging filters (moving average) to reduce the noise level (750Hz – 25Hz).
The transfer function of the mechanical element is designed to avoid resonance effects at
frequencies below the bandwidth of the ASIC.
The availability of new data can be checked in two ways:
•
•
Figure 28: Explanation of data ready interrupt: For a bandwidth of e.g. 1.5kHz the data refresh
cycle takes 330µs to update all data registers. After the final conversion of z-axis the INT pad
will be set high. New data can be read out via interface. The interrupt resets automatically after
read out.
Rev. 1.2
© Bosch Sensortec GmbH reserves all rights even 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 symbol are registered trademarks of Robert Bosch GmbH, Germany.
Note: Specifications within this document are subject to change without notice.
Bit 0 from the LSB data registers is an indicator whether the data have already been
read out or the data are new (Bit0=1) (section 3.5.2).
The interrupt pin can be configured to indicate new data availability (not possible in
parallel to internal interrupt logic). The synchronization of data acquisition and data read
out enables the customer to avoid unnecessary interface traffic in order to reduce the
system power consumption and the crosstalk between interface communication and data
conversion. For a detailed explanation see Figure 3. (section 3.2.10)
INT
INT
INT
T
T
T
330µs at bw=1.5kHz
330µs at bw=1.5kHz
X
X
X
Digital, triaxial acceleration sensor
Y
Y
Y
Data sheet
BMA020
Page 47
Z
Z
Z
T
T
T
X
X
X
Y
Y
Y
Z
Z
Z
Bosch Sensortec
30 May 2008