ADXL346 데이터 시트보기 (PDF) - Analog Devices
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ADXL346 Datasheet PDF : 40 Pages
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SELF-TEST
The ADXL346 incorporates a self-test feature that effectively
tests its mechanical and electronic systems simultaneously.
When the self-test function is enabled (via the SELF_TEST bit
(Bit D7 in the DATA_FORMAT register, Address 0x31), an
electrostatic force is exerted on the mechanical sensor. This
electrostatic force moves the mechanical sensing element in the
same manner as acceleration would, and it is additive to the
acceleration experienced by the device. This added electrostatic
force results in an output change in the x-, y-, and z-axes. Because
the electrostatic force is proportional to VS2, the output change
varies with VS. This effect is shown in Figure 42.
The scale factors listed in Table 14 can be used to adjust the
expected self-test output limits for different supply voltages, VS.
The self-test feature of the ADXL346 also exhibits a bimodal
behavior. However, the limits listed in Table 1 and Table 15 to
Table 18 are valid for both potential self-test values due to bi-
modality. Use of the self-test feature at data rates less than 100 Hz
or at 1600 Hz may yield values outside these limits. Therefore,
the part must be in normal power operation (LOW_POWER
bit = 0 in the BW_RATE register, Address 0x2C) and be placed
into a data rate of 100 Hz through 800 Hz or 3200 Hz for the
self-test function to operate correctly.
3
X-AXIS SELF-TEST HIGH LIMIT
Y-AXIS SELF-TEST HIGH LIMIT
Z-AXIS SELF-TEST HIGH LIMIT
2
X-AXIS SELF-TEST LOW LIMIT
Y-AXIS SELF-TEST LOW LIMIT
Z-AXIS SELF-TEST LOW LIMIT
1
0
–1
–2
–3
1.6
1.8
2.0
2.2
2.4
2.6
2.8
SUPPLY VOLTAGE, VS (V)
Figure 42. Self-Test Output Change Limits vs. Supply Voltage
ADXL346
Table 14. Self-Test Output Scale Factors for Different Supply
Voltages, VS
Supply Voltage, VS X-, Y-Axes
Z-Axis
1.70 V
0.43
0.38
1.80 V
0.48
0.47
2.00 V
0.59
0.58
2.60 V
1.00
1.00
2.75 V
1.13
1.11
Table 15. Self-Test Output in LSB for ±2 g, 10-Bit or Full
Resolution (TA = 25°C, VS = 2.6 V, VDD I/O = 1.8 V)
Axis
Min
Max
Unit
X
70
400
LSB
Y
−400
−70
LSB
Z
100
500
LSB
Table 16. Self-Test Output in LSB for ±4 g, 10-Bit Resolution
(TA = 25°C, VS = 2.6 V, VDD I/O = 1.8 V)
Axis
Min
Max
Unit
X
35
200
LSB
Y
−200
−35
LSB
Z
50
250
LSB
Table 17. Self-Test Output in LSB for ±8 g, 10-Bit Resolution
(TA = 25°C, VS = 2.6 V, VDD I/O = 1.8 V)
Axis
Min
Max
Unit
X
17
100
LSB
Y
−100
−17
LSB
Z
25
125
LSB
Table 18. Self-Test Output in LSB for ±16 g, 10-Bit Resolution
(TA = 25°C, VS = 2.6 V, VDD I/O = 1.8 V)
Axis
Min
Max
Unit
X
8
50
LSB
Y
−50
−8
LSB
Z
12
63
LSB
Rev. 0 | Page 21 of 40
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