BMA020 Bosch Sensortec, BMA020 Datasheet - Page 11

• 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

3.1.3 Bandwidth
These three bits (address 14h, bits 2-0) are used to setup the digital filtering of ADC output data
to obtain the desired bandwidth. A second order analogue filter defines the max. bandwidth to
1.5kHz. Digital filters can be activated to reduce the bandwidth down to 25Hz in order to reduce
signal noise. The digital filters are moving average filters of various length with a refresh rate of
3kHz.
Since the bandwidth is reduced by a digital filter for the factor ½ , ¼, ... of the analogue filter
frequency of 1.5kHz the mean values of the bandwidth are slightly deviating from the rounded
nominal values. Table 4 shows the corresponding data:
Table 4: Settings of bandwidth
At wake-up from sleep mode to normal operation, the bandwidth is set to its maximum value
and then reduced to bandwidth setting as soon as enough ADC samples are available to fill the
whole digital filter.
Important note:
Please refer to the comment in chapter 3 of how to protect bits 5, 6 and 7 when modifying other
bits of register 14h.
3.1.4 Wake_up
This bit (address 15h, bit 0) makes BMA020 automatically switching from sleep mode to normal
mode after the delay defined by wake_up_pause (section 3.1.5). When the sensor IC goes from
sleep to normal mode, it starts acceleration acquisition and performs interrupt verification
(section 3.2). The sensor IC automatically switches back from normal to sleep mode again if no
fulfilment of programmed interrupt criteria has been detected. The IC wakes-up for a minimum
duration which depends on the number of required valid acceleration data to determine if an
interrupt should be generated.
If a latched interrupt is generated, this can be used to wake-up a microprocessor. The sensor IC
will wait for a reset_INT command and restart interrupt verification. BMA020 can not go back to
sleep mode if reset_INT is not issued after a latched interrupt.
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.
bandwidth<2:0>
000
001
010
011
100
101
110
111
Nominal selected bandwidth
Digital, triaxial acceleration sensor
Not authorised code
1500
[Hz]
100
190
375
750
25
50
Data sheet
BMA020
Page 11
Min.
-
bandwidth[Hz]
Mean
1500
188
375
750
23
47
94
-
Bosch Sensortec
30 May 2008
Max.
-