LIS302ALB Datasheet, PDF (10/17 Pages) STMicroelectronics – MEMS motion sensor 3-axis - ±2g analog output piccolo accelerometer

Application hints
4
Application hints
LIS302ALB
Figure 3. LIS302ALB electrical Connection
LIS302ALB
(top view)
Vdd
1
S0
S1
ST
PD
6
Vdd
GND GND
13
100nF 10μF
X
Aux In
GND
Cload z
8
Vout
Y
Optional
Vout z
Z
1
Pin 1 indicator
DIRECTION OF THE
DETECTABLE
ACCELERATIONS
Digital signals
Cload y
Cload x
Optional
Vout Y
Optional
Vout X
Power supply decoupling capacitors (100nF ceramic or polyester + 10μF Aluminum) should
be placed as near as possible to the device (common design practice).
The LIS302ALB allows to band limit Voutx, Vouty and Voutz through the use of external
capacitors. The recommended frequency range spans from DC up to 2.0kHz. Capacitors
must be added at output pins to implement low-pass filtering for antialiasing and noise
reduction. The equation for the cut-off frequency (f_t) of the external filters is:
f_t
=
-------------------------------¹--------------------------------
2π ⋅ R_out ⋅ C_load(x, y, z)
Taking into account that the internal filtering resistor (R_out) has a nominal value equal to
32kΩ, the equation for the external filter cut-off frequency may be simplified as follows:
f_t = -_C----_l--_o---_a---⁵_d---_(μ---_x-^F--_,---_y---_,---_z---₎-[Hz]
The tolerance of the internal resistor can vary typically of ±20% within its nominal value of
32kΩ; thus the cut-off frequency will vary accordingly. A minimum capacitance of 2.5nF for
C_load(x, y, z) is required in any case.
An external capacitor can be added to the Vout pin. Values below 10 pF are recommended.
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