Datasheet
Sensors
36 NXP Semiconductors
MMA8452Q
The threshold values range from 1 to 127 with steps of 0.063 g/LSB at a fixed 8 g acceleration range, thus the minimum resolution
is always fixed at 0.063 g/LSB. If the low-noise bit in register 0x2A is set then the maximum threshold will be 4 g. The
PULSE_THSX, PULSE_THSY and PULSE_THSZ registers define the threshold which is used by the system to start the pulse
detection procedure. The threshold value is expressed over 7-bits as an unsigned number.
0x26: PULSE_TMLT pulse time window 1 register
The bits TMLT7 through TMLT0 define the maximum time interval that can elapse between the start of the acceleration on the
selected axis exceeding the specified threshold and the end when the acceleration on the selected axis must go below the
specified threshold to be considered a valid pulse.
The minimum time step for the pulse time limit is defined in Table 42 and Table 43. Maximum time for a given ODR and
oversampling mode is the time step pulse multiplied by 255. The time steps available are dependent on the oversampling mode
and whether the pulse low-pass filter option is enabled or not. The pulse low-pass filter is set in register 0x0F.
0x26: PULSE_TMLT register (read/write)
Bit
7
Bit
6
Bit
5
Bit
4
Bit
3
Bit
2
Bit
1
Bit
0
TMLT7
TMLT6
TMLT5
TMLT4
TMLT3
TMLT2
TMLT1
TMLT0
Table 41. PULSE_TMLT description
Field Description
TMLT[7:0]
Pulse time limit. Default value: 0000_0000.
Table 42. Time Step for pulse time limit (register 0x0F) Pulse_LPF_EN = 1
ODR (Hz)
Max time range (s) Time step (ms)
Normal LPLN HighRes LP Normal LPLN HighRes LP
800 0.319 0.319 0.319 0.319 1.25 1.25 1.25 1.25
400 0.638 0.638 0.638 0.638 2.5 2.5 2.5 2.5
200 1.28 1.28 0.638 1.28 5 5 2.5 5
100 2.55 2.55 0.638 2.55 10 10 2.5 10
50 5.1 5.1 0.638 5.1 20 20 2.5 20
12.5 5.1 20.4 0.638 20.4 20 80 2.5 80
6.25 5.1 20.4 0.638 40.8 20 80 2.5 160
1.56 5.1 20.4 0.638 40.8 20 80 2.5 160
Table 43. Time step for pulse time limit (register 0x0F) Pulse_LPF_EN = 0
ODR (Hz)
Max time range (s) Time step (ms)
Normal LPLN HighRes LP Normal LPLN HighRes LP
800 0.159 0.159 0.159 0.159 0.625 0.625 0.625 0.625
400 0.159 0.159 0.159 0.319 0.625 0.625 0.625 1.25
200 0.319 0.319 0.159 0.638 1.25 1.25 0.625 2.5
100 0.638 0.638 0.159 1.28 2.5 2.5 0.625 5
50 1.28 1.28 0.159 2.55 5 5 0.625 10
12.5 1.28 5.1 0.159 10.2 5 20 0.625 40
6.25 1.28 5.1 0.159 10.2 5 20 0.625 40
1.56 1.28 5.1 0.159 10.2 5 20 0.625 40